- Animalistic Abomination: A lot of corrupted Gems resemble animals.
- Big-Bad Ensemble: They serve as prominent antagonists throughout the first half of Season 1, until the nature of Homeworld started to come to light during the second half.
- The Blank: Many Gem monsters do not have faces or even facial features, making them appear more alien.
- Fate Worse than Death: "Monster Reunion" reveals that after Homeworld forces left Earth, the Diamonds released something involving a blinding white light that corrupted the minds of every remaining Gem on Earth - Crystal or Homeworld - and forcibly turned them into monsters. Worse, when the Diamonds partially heal Centipeetle she keeps repeating what she was saying right before she was caught up in the corruption attack. This implies that the corrupted Gems are forced to relive the horror of the corruption over and over again.
- Gem Heart: One of the Gems' tasks as self-appointed guardians of Earth is hunting down or defending against monsters that tend to leave behind a gem. They then seal the gem in a bubble and teleport to the temple, keeping the monster from regenerating.
- Gone Horribly Wrong: As it turns out, the Diamond's song was supposed to destroy all the Gems on Earth, not turn them into monsters. Blue and Yellow Diamond are unaware until thousands of years later exactly what they did.
- It Can Think: Despite being portrayed as feral monsters at first, they gradually got smarter as time passed. Justified as its revealed they were once sapient Gems and as shown with Centipeetle, they may still have some vestiges of their mind intact than what it seems.
- Light Is Not Good: As standard per all of Gemkind, these things are made of light and were in fact made into monsters in the first place by a blinding white light.
- Little Bit Beastly: After they are cured most of them retain at least a few of their corrupted form traits, such as Jasper now having permanent horns.
- Magic Is a Monster Magnet: It's theorized that corrupted Gems come to Beach City because they're attracted towards the Crystal Gems.
- Mind Rape: Corrupted Gems are monstrous in body, but that's just because they're shapeshifters who had their mind corrupted. That's why Rose's tears didn't help them, and Steven's only worked partially and temporarily.
- Monster of the Week: Except for Centipeetle and the Alpine Jaspers, they usually only appear for one episode.
- Monstrosity Equals Weakness: They're generally weaker than uncorrupted Gems, with only the largest ones posing much of a threat to seasoned Gem warriors. It's pretty noteworthy that the second Jasper is fully corrupted she goes from an Implacable Man to being One Hit Killed by a comparatively meager attack from Peridot.
- No Body Left Behind: All of the monsters with gems on them disappear in a puff of smoke when they're 'killed', leaving only a gem behind. This similarity to the Crystal Gems turns out to be because the monsters and the Gems are the same thing.
- Not Quite Back to Normal: After being permanently healed of their corruption, the Gems still retain traits of their corrupted forms (ie. Jasper retaining blue spots and horns). Word of God states that the longer a Gem spends corrupted, the more physical traits from their corrupted forms will remain.
- Out of Focus: They gradually decrease in importance as the series goes on and bigger threats come into view - both Homeworld Gems and forced-fusion experiments. "Reformed" is the only second-season episode to prominently feature one. They become important again halfway into season three, though not as antagonists themselves. In season 5, the quest to find a way to cure them becomes Steven's biggest priority, and drives the rest of the conflict up to the season finale.
- Sealed Evil in a Can: Since they all can regenerate given enough time and leave an intact gem, the Crystal Gems bubble them then teleport them to the temple after they've been defeated. This keeps the monsters from regenerating, so long as the bubble isn't breached. "Ocean Gem" reveals they don't just destroy the gems because some of them used to be fellow Crystal Gems.
- Tragic Monsters: They all used to be fully sapient Gems, but now are generally feral monsters. The Diamonds used some sort of weapon during the Gem War and the aftermath caused many of the Gems to be corrupted mentally.
- Viral Transformation: Even without exposure to Homeworld's weapon, a Gem becomes corrupted if they fuse with a corrupted Gem. Most likely this is because corruption is a mental attribute, and Gem fusion has an element of Mental Fusion.
- Was Once a Man: They were once Gems like the Crystal Gems, until they were corrupted somehow.
- We Have Reserves: Some of them were loyal Homeworld soldiers who had the misfortune to be left behind during the evacuation.
- Woobie, Destroyer of Worlds: They were either former Crystal Gems who weren't ready for what was to come next, or Homeworld Gems who couldn't evacuate in time when the "Corrupting Light" was unleashed on Earth during the final hours of the rebellion; now, they prove to be a danger to both humans and the Crystal Gems with their newfound monstrous forms.
Nephrite Facet-413 Cabochon-12, aka "Centipeetle"
Centipeetle: [screech vaguely resembling the word "hi"]
The first corrupted gem to appear in the series, Centipeetle is large, centipede-like Gem monster that attacks the temple in the first episode before becoming more prominent as the series goes on.
- Acid Attack: She can spit acid.
- All Animals Are Dogs: When Steven befriends the smaller version in "Monster Buddies", she acts very dog-like.
- Alternate Identity Amnesia: A complicated case; when partially restored from corruption, Nephrite had a spotty memory of events before and after being corrupted, and eventually remembers her corruption itself. She can also recognize Blue and Yellow Diamond when fully corrupted. When temporarily uncorrupted entirely, Nephrite shows no signs of recognizing Steven or awareness that she was corrupted. Once she is permanently cured, she seems to recognize Steven immediately.
- Anime Hair: Her white hair is very voluminous (and her drawings portray it as very spiky).
- Benevolent Boss: She showed her deep care for her crew by risking Corruption while searching for her crew and then millennia later, frantically searches for her crew when her memories came back.
- Big Creepy-Crawlies: The babies are roughly the size of an average dog while the mother is as big as a house.
- Bizarre Alien Biology: Centipeetle can still eat (or at least taste), despite not having a throat to swallow food with— she just melts food in her mouth with the acid. Not that she needs to eat.Steven: I don't know how you eat with an eyeball in your mouth, but I'm glad you like it.
- Body Horror: Steven's attempt to heal her only works partway, leaving her as a mix of Gem and centipede out of The Fly (1986). She then slowly turns back to a full centipede in a very painful process.
- Bold Explorer: Seems to have been her job before the war broke out.
- The Captain: Had her own ship and her own crew, and by all appearances was a great leader.
- Cute Monster Girl: Steven manages to partially heal her, giving her a somewhat humanoid shape for a while.
- Cute Mute: When not attacking Steven.
- Cyclops: Centipeetle has a single "eye" (actually her gem) in her mouth. In her uncorrupted form, it apparently just functioned as an eye.
- Expressive Hair: Centipeetle's hair changes shape according to her mood.
- Eye Scream: Steven tries to heal her a second time, but since her Gem is her eye, all it does is hurt her.
- Eyes Do Not Belong There: Her eye, which also happens to be her gem, is located in her mouth. This becomes literal as her eye moves into a more conventional position (i.e: out of her mouth) when she gets a more humanoid form, meaning it literally didn't belong there.
- A Father to His Men: During the epilogue of the Gem War, Centipeetle had time to get away on her ship, but she had been separated from her crew and fell behind to look for them. This is how she was corrupted by whatever the Diamonds did.
- Friend or Foe: According to her Troubled Backstory Flashback by crayon, she was on Homeworld's side, but was caught by the Diamonds' "Corruption Nuke". And so was her crew.
- The Good Captain: The nicest high-ranking Homeworld Gem we've met yet.
- Hat of Authority: Her black headdress marks her as a captain. It's her main identification in her drawings.
- Heroic Sacrifice: In "Monster Buddies", she pushes Steven out of the path of a falling rock, getting crushed and returning to her gem.
- Hollywood Acid: She can spit acid that melts through almost anything, but it still doesn't do anything unless it comes in direct contact.
- The Illegible: Subverted. While her "writing" first seems to be a bunch of scribbles, she's actually writing in the Gem language, and according to Pearl, it is "actually decently legible".
- Jaw Drop: Performs a humorous one in Legs From Here to Home World, where Steven takes Yellow and Blue Diamond to see Centipeetles corruption. It takes her a second, but once she notices the Diamonds, Centipeetles jaw goes slack coupled with an awed screech.
- Killed Mid-Sentence: When Blue and Yellow Diamond heal her she is brought back to the exact moment she became corrupted and she keeps repeating: "No, please, no! No, no, we're all gonna be...". It takes Steven's help to snap her into the present, but it doesn't last, reverting entirely the moment they let go.
- Large and in Charge: Is drawn as bigger than her crew, and might be one of the only Gems we've met to have a military rank.
- Latex Space Suit: In a humanoid form, she wears one similar to the spacesuit Pearl wears in "Space Race" and "Back to the Barn".
- Logical Weakness: Is an insect, and is killed by being zapped with electricity.
- Madness Mantra: Upon having her mind and body restored, she is only capable of repeating "No, please, no! No, no, we're all gonna be- No, please, no! No, no, we're all gonna be-". It takes Steven/Pink's powers on top of Yellow and Blue's to make her coherent. Even then, it doesn't last because as soon as they let go, she reverts entirely.
- Mix-and-Match Critters: Her name is a portmanteau of "centipede" and "beetle." She also has a snow-white mane and spits acid strong enough to melt concrete, so you figure out what else went into that mix.
- Monstrous Humanoid: Steven's attempt to heal her only partially succeeds, resulting in her Gemstone migrating back to her face to act just as an eye, and gaining human legs and arms while retaining an insectoid body, as well as healing her mentally, somewhat.
- Mook Maker: As the giant Centipeetle, she can spawn smaller, dog-sized copies of herself.
- No Good Deed Goes Unpunished: She was caught in the Corruption blast because she refused to abandon her crew and stayed to look for them after the evacuation order was given. In other words, she was punished for not being a Dirty Coward.
- No One Gets Left Behind: Remained behind in an attempt to find her crew. Turns out her crew stayed behind to wait for her, too.
- Non-Standard Character Design: She's the only one whose gemstone is changed by and moves around in her construct, instead of being static. This is likely because she'd be blind if it didn't grow a pupil and swivel around to function as her eye. The other Nephrites on her crew are also Cyclopses, but have non-gem eyes and different Gem placement.
- The Noseless: Like Sapphire, she has no nose beneath her large eye.
- One Bad Mother: At first referred to as the 'Mother Centipeetle'. Since she reformed and was no longer a Mook Maker, she's just called "Centipeetle".
- One-Man Army: The giant Centipeetle Mother holds its own against all of the Crystal Gems at once, and would've won if it weren't for Steven's intervention.
- Only Known by Their Nickname: "Centipeetle" is just a nickname the Crystal Gems used for her and her duplicates when talking to Steven (which he sometimes shortens to "Centi"). Steven's partial healing doesn't restore her speech enough that she could say her name (beyond "Gurgle Click Click"), and despite the Gems reading what she wrote, they don't say her name either. She was speculated to be a Nephrite, and as of "Legs From Here to Homeworld", this was confirmed. Specifically, Nephrite Facet-413 Cabochon-12.
- Portmanteau: Her name is a cross between "centipede" and "beetle", two animals she somewhat resembles.
- Scary Teeth: Her teeth are unnaturally sharp, it's implied that these originated from her being corrupted, since other Jades don't have such teeth. Then again, they also have two eyes, so it's hard to tell.
- Sealed Evil in a Can: Like all Gem monsters, after she's destroyed and reverts to a gem, she's sealed in a bubble and teleported to the temple for safekeeping. Becomes closer to Sealed Good in a Can after her Heroic Sacrifice, since Steven may have the ability to heal her. Later, she joins the two crew members who remained behind in a sealed chamber in their old ship.
- Shout-Out: Her gem resembles a Poké Ball, and in "Monster Buddies", Steven befriends and tames her by showing kindness to her, much like a Trainer would raise a Pokémon. Her facet number (413) is an Arc Number in Homestuck.
- Sleep-Mode Size: Upon regenerating in "Monster Buddies", she takes on a tiny form even smaller than her mook copies. After being partially healed but reverting to corrupt form, she regains some size, but is still nowhere near as big as her first appearance.
- Starter Villain: As a Gem monster, she shows up in the first episode as an enemy that was dangerous to Steven but that he could help defeat even before he had any powers.
- Super Spit: Acidic.
- Tastes Like Friendship: Steven manages to tame her somewhat by feeding her chips.
- Trademark Favorite Food: Chaaaaps. She likes them so much that Steven left a bag of Chaaaaps bubbled next to Centipeetle's gem in the Burning Room.
- True Companions: Her whole crew was willing to risk to a Fate Worse than Death to try and find each other, then still waited for their captain for thousands of years.
- Undying Loyalty: Even after being cursed to become a mindless monster for millennia, upon being healed she apologizes for not escaping the corruption attack in time and happily assumes Rose was shattered.
- The Unintelligible: To Steven anyway. She seems to be able to communicate with her crew.
- Was Once a Man: While reforming, Centipeetle briefly takes on a humanoid form, alluding to the fact that all Gem Monsters used to be normal Gems. Later confirmed in "Ocean Gem."
- You Are Number 6: After she is (temporarily) uncorrupted, she immediately identifies herself as Nephrite Facet-413 Cabochon-12.
A Gem monster with an affinity for glowing seaweed. Its screams can cause tremors. Art & Origins revealed that the Crewniverse named her "Crunchrock" during a game while designing her uncorrupted form.
- Cute Monster Girl: Her true form is a cute little humanoid slug person.
- Early Installment Weirdness: Her concept art for her uncorrupted form looked like a fusion of Jasper and Topaz in a tutu. When she's actually healed in the show she looks like a cute little gelatinous bipedal cyclops with a seashell on her head.
- Horror Hunger: Implied; it's a Gem, so it does not need to eat, but it keeps obsessively hunting down and trying to eat glowing things.
- Knotty Tentacles: It's tricked into tying itself around the dock, then collapsing it on itself.
- Make Me Wanna Shout: Its screams shake the Earth from miles away.
- Monster of the Week: In "Bubble Buddies".
A white gem found in the center of the Pyramid Temple. It operates the room-switching mechanism, causing intruders to endlessly wander through rooms that all lead back to the same central chamber.
- Living MacGuffin: The Crystal Gems go through quite a lot of trouble in "Serious Steven" to collect it, even collecting a key to enter the temple and navigating its Death Course. We're only given an apparent reason when the Gem monsters turn out to be corrupted Gems they're trying to bubble, assuming it's corrupted.
- Living Structure Monster: The central chamber of the pyramid appears to be made of Hard Light similar to a Gem's body, as the spinning platforms powering the room mechanism dissolve into specks of light that were absorbed into the gem. Other parts seem to be stone, as the pieces were still around afterward.
- Load-Bearing Boss: Removing the gem from its place dissolved part of the temple and blew up the rest.
- Sealed Evil in a Can: The Pyramid Temple seems designed to keep this Gem in and/or intruders out. It's unknown if said Gem was loyal to the Homeworld or Crystal Gems previously, but it's most likely corrupted now.
A gem embedded in a pillow that, upon contact with sand, starts creating random structures out of it. It otherwise remains dormant.
- Dishing Out Dirt: If it's in physical contact with sand, it will build structures around itself like walls and spires and also whip up a sandstorm.
- Was Once a Man: An even more extreme case than most corrupted Gems, as it doesn't outwardly appear to be sapient, or even alive. It's not entirely clear if it's a corrupted Gem or a device powered by an uncorrupted Gem.
Cave Creature/Gem Driller
A spike covered creature that inhabits a cave. Can send out Drill Parasites.
- Attack Drone: The drill is shoots off can act independently. And, unlike most constructs created by Gems, they do not disappear when the Gem's body is destroyed or even when the gem itself is stuck in a bubble.
- Spikes of Villainy: The top of its body is covered in spikes.
- This Is a Drill: Has a giant one at the bottom of its body. The drill parasites can also assume this form.
A giant bird that hangs around the Sky Spire. Its innards are lined with gems.
- Asteroids Monster: Opal tears the bird apart, but the pieces reform into dozens of winged beaks that fly after her.
- Eyeless Face: There are no eyes visible on its head or anywhere else.
- Feathered Fiend: It flies around trying to eat everything that moves.
- Fusion Dance: They appear to be many similar corrupted Gems fused into one. Confusingly, the numerous gems inside of it are bubbled (and thus couldn't have been projecting bodies), don't look the same as the gemstones the small birds had, and aren't there when the big bird split apart.
- Horror Hunger: Like the worm monster, it keeps trying to eat everything even though it doesn't need to eat anything to survive.
- Stomach of Holding: Its insides are full of things that is Swallowed Whole, including many bubbled gems.
- Was Once a Man: Likely, though unlike the other pre-"Ocean Gem" Gem monsters, it was not seen in Pearl's explanation.
Geode Beetles of Heaven and Earth
Two Gem beetles, the Heaven Beetle and Earth Beetle, collected from their homes as the driving plot of "Giant Woman".
- Ambiguously Gay: When they're purified of the corruption in "Change Your Mind", the one that became the Earth Beetle plants a kiss on the Heaven Beetle's cheek.
- Baleful Polymorph: Their corruption just seems to have stuck them in the form of beetles with full sapience. The Heaven Beetle at least has a room with miniature furnishings, bongos to play, and even a game system.
- Damsel in Distress: The Heaven Beetle was eaten by the Big Bird. They were both cloistered in their respective temples for some as yet unknown reason.
- Lilliputians: Being purified of the corruption in "Change Your Mind" shows that their size is not part of their corruption—they're naturally that small.
- Meaningful Name: The Heaven Beetle is high up in the air, and the Earth Beetle is underground.
- Super Toughness: The Earth Beetle is at the bottom of a boiling lava lake, which only Garnet can swim in. The Heaven Beetle at least was being gnawed on by a goat without injury.
- Was Once a Man: They are also corrupted Gems.
A giant pufferfish monster.
- Astonishingly Appropriate Appearance: Watermelon Tourmaline has a green and pink color motif and a spherical shape.
- When she appears uncorrupted at the end of "Change Your Mind," she looks very much like a humanoid pufferfish.
- Blow You Away: Its main power is shooting out an unending stream of high-pressure air.
- Hellish Pupils: Its green pupils are diamond-shaped.
- Monster of the Week: Of "Beach Party".
- Painful Pointy Pufferfish: A boogie board gets impaled on one of its spines. Ironically, it's defeated when punctured by an equally pointy glass shard.
- Stealth Pun: Watermelon Tourmaline was smashed during the Beach Episode. Her gemstone also resembles a watermelon slice.
- Was Once a Man: Word of God has even stated what Gem it is.
A Gem monster made of ice that resides in the same cavern as the Shooting Star. Art & Origins revealed that the Crewniverse named her "Chazuski" during a game while designing her uncorrupted form.
- An Ice Person: The monster is made of ice and lives in a cavern full of snow and icicle-like formations.
- An Ice Suit: Her true form is a little blue fairy-like creature wearing a parka.
- Black Eyes of Crazy: Inverted. She gains black sclera with white pupils when she's uncorrupted.
- Cephalothorax: It's a giant chunk of ice with a face on it, with arms and legs.
- MacGuffin Guardian: It prevents the Crystal Gems from reaching the Shooting Star, a powerful artifact found deeper inside the mountain.
- Monster of the Week: Of "Monster Buddies", though its bubbled gem makes a few minor appearances.
- Shout-Out: Its body bears resemblance to a Freezie from the Super Mario Bros. franchise, down to the jagged mouth.
A Gem monster lurking on Mask Island.
- Invisibility: Completely invisible except for its gem.
- Killer Gorilla: Its silhouette that can be seen once it gets some mud on it resembles one, with its human-like face, large arms that are used in walking, and hunched back.
- Monster of the Week: In "Island Adventure".
- See the Invisible: It becomes visible once its face is covered in mud.
- Stealth Expert: Being invisible helps. The Crystal Gems assumed it had escaped from Mask Island.
A Gem monster resembling a Topaz that has been merged with the lighthouse on top of the Temple.
- Living Structure Monster: A Gem that is merged with the lighthouse above the temple, and manifests a giant maw in the wall.
- Mental Picture Projector: Creates a hologram of how Lars and Ronaldo's friendship fell through, and in the process showing how it was mad at Lars for "attacking" it.
- Mind over Matter: It has telekinetic powers that it uses to attack the group, throwing around objects, animating scarecrows, and causing the building's very structure to attack them.
- Monster of the Week: Of "Horror Club".
- Revenge: It is attacking the group because Lars carved his name in the wall as a kid.
- Woobie, Destroyer of Worlds: Steven describes it as feeling hurt and trapped.
A random Gem monster that Garnet is seen fighting in "Love Letters". It makes a brief appearance in "Earthlings" as one of the monsters Jasper captured for her army.
- Big Creepy-Crawlies: It resembles a tardigrade and is about the size of an adult human.
- The Cameo: Another one made a short appearance in "Earthlings".
- Seldom-Seen Species: It is based on a tardigrade.
- Slime Girl: Her uncorrupted form looks like a chubby snowman made of blue jello.
- Stealth Pun: "Water bear" is one name for tardigrades, but this creature looks as if it is actually made of water.
A plantlike Gem monster that was creeping around the temple, and repeatedly poofed Amethyst. Was possibly taken care of offscreen after the Hot Dog Duffel Bag short. Art & Origins revealed that the Crewniverse named her "Starbite" during a game while designing her uncorrupted form.
- Combat Tentacles: Uses its vines to grab and constrict its enemies.
- Fast Tunnelling: It can quickly move through the ground and create tunnels that go to different parts of Amethyst's room.
- Hero Killer: Repeatedly forced Amethyst to regenerate.
- In-Series Nickname: Steven came up with the name. While Amethyst disliked the name, it stuck.
- Mix-and-Match Critter: It has some sort of plant/cephalopod hybrid.
- Tentacle Rope: How it keeps making Amethyst "poof".
- When Trees Attack: Has a plantlike appearance, with a flower as a mouth and Combat Tentacles.
A large Gem creature residing on Beach City's beach. The Quidd trading card app◊ labels her gem as Aventurine.
- Cyclops: It has one eye.
- Expy: Ian Jones Quarterly admitted on a podcast that he'd subconsciously made her uncorrupted form one of Darrell from OK K.O.! Let's Be Heroes.
- Giant Enemy Crab: Something like five meters tall.
- Go for the Eye: Its obvious weak spot.
- Mini Mook: A tiny one grabbed Ronaldo's hand.
A Gem monster that had attacked William Dewey's ship long ago. Represented in the play with a silhouette and cardboard tentacles.
A pair of enormous quadrupedal Gem monsters with long white manes, found in the Great North. One, the Orange Great North Monster, has three horns and shades of orange skin. The other, the Snow Monster, has two horns and teal skin with circular patches of pink.
- The Bus Came Back: They wash back ashore in "Crack the Whip". Amethyst poofs one and it gets sent to the temple, but Jasper attacks with the other, and leaves with its gem. The Orange Great North Monster reappears in "Made of Honor" when Bismuth sets her free, unaware that she's no longer the Biggs she knew.
- Eyeless Face: Their heads have no eyes or nose; they're basically just a mouth with horns. Consequently, they appear to go mostly by sound.
- Fusion Dance: Jasper forces the Snow Monster to fuse with her in an attempt to go One-Winged Angel against Smoky Quartz. It backfires, BIG TIME.
- It Can Think: They've retain enough intelligence to communicate with each other and split up while fleeing to throw off their pursuers.
- Mighty Roar: One lets out a roar that shakes the screen while spitting out a steam cloud.
- Non-Malicious Monster: They actively avoid Steven, Connie, and Pearl, because they're actually running away from Jasper. One only attacks Steven and Connie when it's cornered and Connie nervously draws her sword. They live in a remote area, so they may not have been a danger to anyone if they weren't being hunted down.
- Palette Swap: Other than number of horns on each, and lack of claws on the wavy-skinned one, their appearance only differs in color.
- The Power of Friendship: Seem to be looking out for each other.
- Was Once a Man: Their white manes similar to Jasper and Amethyst, along with their coloration, strongly suggest that they're other Quartz Gems. Their colour pattern suggests that they once were an Ocean Jasper and Biggs Jasper. Jasper herself later confirms that the green one was indeed another Quartz, but doesn't specify a specific type. Jasper's corrupted form looks extremely similar, implying they are indeed types of Jasper. This was later confirmed at NYCC 2016. The Orange Great North Monster is confirmed in "Made of Honor" to be the former Crystal Gem Biggs Jasper.
A blue ball-shaped Gem monster from the Beta Kindergarten, with bird legs, a large mouth with three tongues, and three small eyes on either side of her gem.
- Armless Biped: Has two long, birdlike legs and no arms.
- Cephalothorax: She's a furry ball with a face and bird legs.
- Expy: She acts quite a lot like the Road Runner from Looney Tunes, and looks like a monstrous version of Sanic. Her constantly outsmarting Peridot coupled with her birdlike appearance and tendency to attack Steven with her foot claws also makes her resemble a more comical version of the raptors from Jurassic Park.
- Extra Eyes: She has six small yellow eyes with square pupils, three on either side of her gem.
- Feathered Fiend: Vaguely resembles a bird.
- It Can Think: Manages to outwit Peridot and Steven when they tried Peridot's third "Peri-plan" by sneaking up behind them and startling them with a sudden noise. Then she taps the boulder they planned to drop on her, dropping it on them instead.
- Lightning Bruiser: Not only does she run fast, she beats up Peridot and Steven several times with little effort and can tow Gems without losing speed.
- Monster of the Week: Of "Kindergarten Kid".
- Overly Long Tongue: She has three of them, which are so long they can't fit in her mouth, and she constantly sticks them out into the air.
- Raptor Attack: Her feathers, bird feet, sharp teeth and "It Can Think" qualities are reminiscent of this trope.
- Uncertain Doom: The bubble that contained her gem was stored at the barn, which is now destroyed since Lapis dropped it on Blue Diamond. For what it's worth, Joe Johnston suggested that her gem didn't remain in the barn for long, with Peridot keeping it as a trophy for a few days before sending it to the Burning Room in the Temple.
- Wheel o' Feet: She's shown having these in a few scenes, emphasizing her being a Road Runner Expy.
- Cephalothorax: Basically a giant head with four root-like limbs (plus an arm for a tongue).
- More Teeth than the Osmond Family: Most of its body is taken up by a mouth full of pointed teeth along with two buck teeth.
- Planimal: It's like a giant turnip mixed with the head of a star-nosed mole, with the flower as the "nose".
- Walking Spoiler: The plot of "Back to the Kindergarten" is based on Steven, Amethyst, and Peridot mistaking its protruded nose for a flower and thinking the Kindergarten could support life again.
Cluster GemsCreatures created by Homeworld thousands of years ago, by means of sticking Gem Shards together and incubating them.
Collected masses of gem shard body parts resulting from fusing several Crystal Gems together. In the Kindergarten control room, there are several small ones consisting of two limbs or hands, plus a larger one made of several arms and legs forming a single hand. More escaped from the subterranean chamber, including two humanoid but still very monstrous clusters that wandered outside the Kindergarten entirely.
- Artificial Zombie: They were created by fusing the gem shards of broken Crystal Gems.
- The Blank: One of the clusters in the hospital has what could vaguely be called a head, but it still doesn't have a face, just a stump with its gemstone in the center.
- Body Horror: The in-show zenith of the trope.
- Body of Bodies: When one first tries to form a body, it produces four different humanoid silhouettes merged by the spine and hips, screeching in agony. It then turns into a hand made of arms and legs.
- Came Back Wrong: Their attempts to reconstruct their bodies don't go well.
- Condemned Contestant: The Crystal Gems were used as subjects as punishment for their rebellion.
- Cyclops: One of the Kindergarten Clusters, the most humanoid seen thus far, has a face with only one eye.
- Eyes Do Not Belong There: The Hand Cluster has four eyes on the front of its body, which is in the form of the palm of a giant hand, laid out in a rotational pattern. Another in the Kindergarten has an eye inside its mouth, while yet another consists of a huge red eye with limbs hanging off the socket.
- Flawed Prototype: All the human-sized fusions are ones that hatched early, hence why they aren't terribly threatening. The Cluster, which has yet to hatch, is comprised of millions of shards and will destroy Earth just by hatching.
- Fusion Dance: Fusing the gemstones themselves together caused the Gems they comprise to become permanently bonded into a single, twisted, tortured creature. Unlike a true fusion, they are only merged in body, not mind. Shards in the same cluster aren't even capable of noticing each other without outside assistance.
- Hologram Projection Imperfection: As the Hand Cluster forms its body, it glitches twice before settling on a shape, a much more terrifying version of the way the Gems cycle through their old forms before choosing a new one.
- I Have Many Names: There isn't really a single name for these things inside or outside of universe. Dialogue in-show has them called "gem mutants", "gem/fusion experiments", "clusterlings" and "prototypes". The voice credits call them "monsters" and the ones in the hospital "patients". Model sheets have labelled them as both "clusters" and "mutants". In the Keep Beach City Weird book, Ronaldo calls them "limb zombies" because he thinks they're just "regular" zombies, not Non-Human Undead.
- Leitmotif: Gem Shards. A horrifying piece that sounds like a bunch of disconnected instruments and music styles forced together to become a discordant, tortured whole; not unlike the creatures themselves.
- Light Is Not Good: Same reasons as regular Gem monsters, except now their Hard Light frames are composed of pure Body Horror.
- Magic Is a Monster Magnet: Cluster Gems seek out regular gems because of their shards' desire to become whole.
- Merging Mistake: They are the result of trying to artificially fuse shattered Gems together.
- Monstrosity Equals Weakness: The same factors that make them so horrifying also make them fairly weak: the ones in the Kindergarten control room could barely even move. The ones in the hospital seem significantly weaker than typical gems, as Connie and Steven were both able to overpower one with little difficulty, and the Crystal Gems easily dispatch numerous ones on the surface of the Kindergarten.
- Multi-Armed and Dangerous: Though not especially threatening, some of the smaller ones in Facet Five are nothing but arms, and the Hand Cluster has four that serve as fingers. The Hospital and Kindergarten Clusters, which are far more aggressive and dangerous, play the trope straight.
- No Zombie Cannibals: They'll attack whole gems out of a desire to be whole, yet they ignore each other.
- Nonhumans Lack Attributes: The larger ones have been seen wearing clothes (medical gowns put on them by humans in the case of the ones in the hospitals), but they don't really have anything to cover up◊.
- Non-Human Undead: They're essentially alien Flesh Golems, except the "flesh" is actually Hard Light.
- Non-Malicious Monster: Despite their appearance, none of the ones in the Kindergarten control room seem to actually be violent. When the Hand Cluster grabs Garnet, it seems less like it's attacking and more like it's clinging to her, possibly because the Crystal Gems it is made from recognize her. Later ones are more aggressive. Peridot later explains that they are simply so desperate to find their missing fragments that they seek out other Gems in the hopes of finding them. The Keep Beach City Weird book mentions they've been sighted by humans, but makes no mention of attacks, suggesting they're benign when not in the presence of other gems.
- Outside-Context Problem: The Gem Cluster mutants were a completely unexpected threat to the Crystal Gems, who had no idea they even existed or that Homeworld had been making them right under their nose until they stumbled on them by accident.
- Sealed Evil in a Can: They were all sealed away in the containers they were grown in, on the lowest level of the Kindergarten. Peridot opened the containers to check their growth but didn't seem to bother securing them. Many escaped to the surface of the Kindergarten with some wandering miles away into human-inhabited space.
- Shown Their Work: Keeping with the series' motif of real-world gem references, gem clusters can actually happen in real life; underground heat and pressure can occasionally fuse gems together, though fused gems of different kinds are rare.
- Tragic Monster: The Cluster Gems attack other Gems with such ferocity not out of malicious intent, but because they want to find their missing shards so they can be whole again.
- Two Beings, One Body: Many beings, in this case; unlike other fusions, they didn't agree to what they were doing and are, at least as far as we know, stuck that way forever.
- Undead Abomination: They are the shattered remains of gems remade into mindless monsters.
- Vagina Dentata: The large red cluster in the Kindergarten has a vertical fanged mouth which greatly resembles this. Inside the mouth? An eye.
- Walking Spoiler: They're a secret the Homeworld managed to keep from the Crystal Gems despite being right under their noses for thousands of years.
- Wall Crawl: The six-armed hospital cluster pursues Steven and the Maheswarans by using two of its arms to walk across the ceiling.
- Was Once a Man: Every one of the Gem fragments used to make them used to be a Crystal Gem.
An experimental fusion formed of millions of gem shards, this immense Cluster Gem lies deep within the Earth.
- Adorable Abomination: The first thing it does after forming and fending off Yellow Diamond's ship is give Steven a thumbs-up.
- Astonishingly Appropriate Appearance: Its arm form is made of layers of stratum that greatly resemble the musculature of a human arm.
- Backup from Otherworld: In "Reunited", it essentially serves this role by virtue of being composed of the shards of countless shattered Crystal Gems who return to aid their surviving comrades against the Diamonds. This is invoked in its formation, which gives the appearance of countless wailing spirits rising from the grave.
- Beneath the Earth: It's buried deep inside the Earth's mantle.
- Big Damn Heroes: When they're awakened by the Diamonds in "Reunited", they choose to manifest themselves as a huge humanoid arm coming from the ground, and they fight against Yellow Diamond while the Crystal Gems are busy fighitng Blue Diamond. Eventually, they manage to destroy both of their spaceships before returning to their bubble.
- Body Horror: When it forms in "Reunited", the part we see resembles a skinless human arm.
- Creepy Good: When forced to emerge, their wailing ghostly projections form what looks like a skinless, disembodied human arm... which gives the Crystal Gems a thumbs up and helps them fight!
- Doomsday Device: The Cluster Gems are just a few shards clumped together. The Cluster itself is millions of shards incubating in the Earth's core, and its physical form will crack the Earth like an egg when it finally matures. Steven helping and befriending it results in it rejecting this purpose and actively helping save the planet.
- The Dreaded: The threat of The Cluster is enough that the Crystal Gems and Peridot (reluctantly) join forces to stop it.
- Earth-Shattering Kaboom: If it constructs a body, it will destroy the Earth. This is only if it forms completely, forming just an arm is fine.
- Eldritch Abomination: Its true form as depicted in the official artbook as linked below is a titanic, vaguely feminine monstrosity with Too Many Mouths and Eyes where they do not belong. This horrific form might still be canon given the appearance of its arm in "Reunited", so it's a good thing it's on the Crystal Gems' side and no longer wants to form.
- Everything's Better with Sparkles: Eldritch abomination or not, the cluster's gem core is visually stunning.
- Evil Is Bigger: The form it would take upon hatching is expected to be several times bigger than the Earth. When it partially manifests in "Reunited", it's no longer evil, but its arm is miles long.
- Genius Loci: The form it's expected to take after hatching is at least planet-sized.
- HeelFace Turn: Although it wasn't technically villainous to begin with, Steven manages to befriend it and it chooses to remain in the Earth's core as a community unto itself to feel whole instead of forming. When it reappears in "Reunited", it only forms an arm and fights Yellow Diamond's ship to help the Gems.
- Helping Hands: It takes a partial form in "Reunited" as a giant humanoid arm.
- Heroic RRoD: After defeating Yellow Diamond's ship in "Reunited", its form starts glitching, and it returns to its bubble.
- Hulk Speak: It does indeed tend to use fragments.
- Kaiju: Released pictures from the official artbook reveal its formed size would be colossal◊.Just its arm forming in "Reunited" is miles long and equal in size to the Diamonds' personal ships.
- Leitmotif: A meandering, disconnected series of tones with no unifying melody. It can be lonely and alien or a thunderous blast of sound at a moment's notice. Steven's intervention makes the tones harmonise and become gentle and soothing. It gets a second remix during its appearance in "Reunited" where it becomes a heroic battle theme.
- Little "No": Its response to being told that forming would destroy the Earth.
- Mind Hive: The minds of the Cluster's body share a body, but individual shards seem to have barely realized the others were in there with them, despite their desperation to feel whole, until Steven introduced them. Played straight in the end when Steven makes them aware of each other, then convinces them to feel whole by communicating with each other instead of forming and destroying the Earth. When it's finally forced to form, it has gained enough of mind to only form an arm and side with the Crystal Gems.
- Non-Malicious Monster: It has no desire to destroy the Earth, it merely wants to be whole. Steven convinces it to find company in its pieces, and manages to help it bubble itself when it can't keep itself from forming. Solidified in "Reunited" when its gained enough control to only manifest as an arm and promptly turns against the Diamonds to protect the Earth.
- Outside-Context Problem: Even more so than the Cluster Gems since the Cluster has been incubating for 5,000 years since the war ended. The Crystal Gems would have had absolutely no idea that it existed until it hatched (and by then it would have been too late) if Peridot hadn't told them. Turns out to be this for the Diamonds in the end: the idea it could choose how much of itself to manifest and turn against them without destroying the Earth takes them by surprise and takes Yellow Diamond's ship completely out of the fight.
- Spell My Name with a "The": While the other forced-fusion experiments are called Clusters (model sheets call the Kindergarten control room ones "X Cluster", where X is the parts they're made of), this one is called the Cluster to differentiate.
- Sympathetic Sentient Weapon: Intended as a Doomsday Device, but made up of millions of still-conscious Gem shards.
- Tragic Monster: Like the smaller prototype Cluster Gems, the Cluster has no malicious intent. The shards constituting it merely want to find their missing pieces so they can be whole, and are horrified when they find out forming would destroy the planet.
- Turned Against Their Masters: It was created by the Diamonds to be a super-weapon, but its first act after forming is punching Yellow Diamond's ship and destroying it.
- Voice of the Legion: Being composed of millions of gem shards, it naturally speaks with millions of voices at once.
- Walking Spoiler: First mentioned in the season one finale, there was basically no indication of what it was until near the middle of season two. The Reveal that it's a gigantic Gem Cluster fusion that's been incubating inside the Earth's core since the war began is a huge twist that causes it to immediately dominate the plot.
- Woobie, Destroyer of Worlds: The Cluster doesn't actually want to destroy anything, it just wants to be something.