Crystal Gems (Steven Quartz Universe | Garnet | Amethyst | Pearl | Rose Quartz | Connie Maheswaran | Peridot | Lapis Lazuli) | Gem Fusions | Homeworld Gems | Diamond Authority (Yellow Diamond | Blue Diamond | Pink Diamond | White Diamond) | Yellow Diamond's Court (Jasper) | Blue Diamond's Court | Spinel | Off Colors | Gem Monsters | Little Homeworld | Humans (Greg Universe | Lars Barriga | Sadie Miller) | Other | Garnet's Universe
Corrupted GemsCreatures who, like the Crystal Gems, have gems on their bodies, and are in many ways similar to the Gems, because they are Gems.
- 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.
- FaceMonster Turn: Any Gem caught by the Diamond's attack was morphed into a feral creature, who usually lash out at random places or things they consider a threat.
- 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: 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 being cured, most of them retain at least a few of their traits while corrupted, such as uncorrupted Quartzes now having 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 green 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.
A white gem found in the center of the Pyramid Temple. She operated the room-switching mechanism that caused intruders to endlessly wander through rooms that all lead back to the same central chamber.
- Ambiguous Situation: In the show itself, it wasn't clear if she was a corrupted gem, a non-corrupted gem, or completely non-living device. The show's former co-lead writer said online that it was a corrupted Gem, though he later deleted that post, leaving it up in the air. A concept design for her actual form was in the End of an Era artbook alongside other Corrupted Gems, confirming she was indeed one.
- Floating Limbs: The concept design for her uncorrupted form has her arms and head detached from her body and floating above where her shoulders and neck would be.
- Living MacGuffin: The Crystal Gems go through quite a lot of trouble in "Serious Steven" to collect her, 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.
- 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 her place dissolved part of the temple and blew up the rest.
- One-Shot Character: Only appears in "Serious Steven".
- 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 she most likely became corrupted at some point.
A gem embedded in a pillow that, upon contact with sand, starts creating random structures out of it. She otherwise remains dormant.
- Ambiguous Situation: The show's former co-lead writer said online that it was a corrupted Gem, though he later deleted that post, making it ambiguous if it's a corrupted Gem, a device powered by an uncorrupted Gem, or not alive at all. A design for her actual form was showcased in the End of an Era artbook alongside other Corrupted Gems, confirming she was indeed one.
- One-Shot Character: She only appeared in "Steven's Lion".
- Sand Blaster: If she's in physical contact with sand, it will build structures around itself like walls and spires and also whip up a sandstorm.
A spike covered corrupted Gem that inhabits a cave. Can send out Drill Parasites.
- Attack Drone: The drill she shoots off can act independently. And, unlike most constructs created by Gems, they don't disappear when the Gem's body is destroyed or even when the Gem herself is put in a bubble.
- One-Shot Character: Only appears in "Arcade Mania", though her and the parasites are part of the scenes that go by while Pearl explains what Corrupted Gems are.
- This Is a Drill: Has a giant drill at the bottom of her body. The drill parasites can also bring their points together to use as a drill.
A giant bird that hanged around the Sky Spire. Her 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 splits apart.
- Horror Hunger: Like the worm monster, it keeps trying to eat everything even though it doesn't need to eat anything to survive.
- One-Shot Character: Its/Their only appearance was in "Giant Woman"
- Stomach of Holding: Its insides are full of things that is Swallowed Whole, including many bubbled gems.
- Was Once a Man: It's most likely a fusion of many corrupted Gems, though unlike the other pre-"Ocean Gem" Gem monsters, it was not seen in Pearl's explanation. A concept for her uncorrupted design shown in the End of an Era art book resembles a single Gem, further complicating things.
A Gem monster that lurked on Mask Island.
- Invisibility: She's completely invisible except for her gemstone.
- Killer Gorilla: Her silhouette that can be seen once she gets some mud on herself. She resembles a big gorilla, with an ape-like face, large arms that are used in walking, and hunched back.
- One-Shot Character: Only appears in person in "Island Adventure", though her gemstone cameos in "Change Your Mind".
- See the Invisible: She becomes visible once her body gets covered in mud.
- Stealth Expert: She's able to be stealthier than most corrupted Gems because of her invisibility. The Crystal Gems assumed she had escaped from Mask Island because of it.
A corrupted Topaz that was trapped inside the lighthouse on top of the Temple. Holds a big grudge against Lars.
- Living Structure Monster: Due to being trapped inside the walls for so long, she gained control of the lighthouse itself, certain objects inside and part of the surrounding area outside. Lars coming closer to where she was stuck angered her enough to create a giant maw in the wall.
- Mental Picture Projector: Creates a hologram of how Lars and Ronaldo's friendship fell through, in the process showing how she was mad at Lars for "attacking" her.
- Mind over Matter: She has telekinetic powers that she uses to attack the group, throwing around objects, animating scarecrows, and causing the building's very structure to attack them.
- One-Shot Character: Only appears in "Horror Club", though Ronaldo throwing Lars into her mouth is among Steven's flashbacks in "Growing Pains".
- Revenge: She attacked the group because Lars carved his name in the wall as a kid.
- Woobie, Destroyer of Worlds: Hunted the group all night and tried to murder Lars, but once Steven grabs her gemstone he realizes it's because she's felt hurt and trapped for so long.
A random Gem monster that Garnet is seen fighting in "Love Letters". Another of the type 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".
- Chuck Cunningham Syndrome: The only one of the Corrupted Gems shown in "Change Your Mind" to not make a reappearance in the movie or Steven Universe: Future.
- Seldom-Seen Species: She 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 taken care of off-screen after the "Unboxing" short.
- Combat Tentacles: Uses her vines to grab and constrict her enemies.
- Fast Tunnelling: She 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 Slinker". While Amethyst disliked the name, it stuck. A name to go with her uncorrupted concept art was revealed in the End of an Era artbook.
- Mix-and-Match Critter: Her corrupted form is some sort of plant/cephalopod hybrid.
A Gem monster that had attacked William Dewey's ship long ago. Represented in the play with a silhouette and cardboard tentacles.
A blue ball-shaped Gem monster captured by Jasper for her army, it is poofed when Peridot makes it fall off a cliff and gets bubbled shortly after.
- 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.
- 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.
- One-Shot Character: Her only appearance is in "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 was destroyed when Lapis dropped it on Blue Diamond. 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.
A plant-like corrupted Gem that made her home in the Prime Kindergarten before being discovered by Steven, Peridot, and Amethyst.
- Cephalothorax: Basically a giant head with four root-like limbs, in addition to an arm for a tongue.
- More Teeth than the Osmond Family: Most of her body is taken up by a mouth full of pointed teeth and two buck teeth.
- One-Shot Character: Only appears in "Back to the Kindergarten".
- Planimal: She's 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 her protruded nose for a flower and thinking the Kindergarten could support life again.
- Ambiguous Situation: It's left unclear if Steven turning into the monster was the mere result of his shapeshifting abilities reacting to him feeling like a monster, similarly to the time he felt old on his birthday and started aging rapidly, or a form of corruption akin to the one the Diamonds inflicted on the gems on Earth.
- Animalistic Abomination: A huge reptilian creature born from Steven's fear and self loathing.
- Attack of the 50-Foot Whatever: The largest single being introduced in the series, it towers over even White Diamond, and is about twice as tall and five times bigger than her. The only thing bigger than it is the Cluster.
- Broken Tears: When the Crystal Gems, Diamonds, Spinel, Greg, the Cluster and Connie finally get through to him with their love, he starts openly weeping.
- Early-Bird Cameo: The monster is present in the antagonists shot from the intro of Steven Universe Future from the very beginning, but he's not properly introduced until the second-to-last episode, where his true nature as Steven's monstrous form is revealed.
- FaceMonster Turn: He's Steven, corrupted by his unresolved trauma and self-loathing boiling over.
- Final Boss: He's the final antagonist the Crystal Gems have to face, being Steven himself.
- Glowing Eyes of Doom: He ominously does this in the intro, pointing his significance above the other antagonists. He also does it in his featured episode right before he releases a shockwave powerful to knock everyone down, even the Diamonds and their ship.
- His Own Worst Enemy: The result of having an unsure thoughts of his future combined with his past trauma transformed Steven at the moment his anger provoked his meltdown.
- "I Know You're in There Somewhere" Fight: The entire objective of the Crystal Gems during the fight is to find a way to reach the true Steven beneath the monster and calm him down from his rampage. Stopping Steven by hurting him is left out of the question by everyone.
- The Juggernaut: The creature is near unstoppable; not even Lapis with her powerful water bindings, the Diamonds with their new-found powers or the Cluster itself are able to hold him for too long.
- Kaiju: He's as big as the mountain that the temple was built into.
- Long Neck: Has a very long, serpentine neck, adding to his reptilian appearance.
- The Mind Is a Plaything of the Body: White Diamond mentions that this monster "is not Steven anymore" when trying to link with his mind, and Sapphire confirms that if they don't do something soon, he would be trapped in that form and state of mind forever.
- Make Me Wanna Shout: The only ability Steven uses in this state is a screech, powerful enough to knock over all three of the Diamonds and their ship, dispel Lapis's water chains, and even force Garnet to defuse (if only for a moment).
- Morphic Resonance: The shapes of his horns evoke Steven's hair, the upper half of his head is notably similar (especially the nose and eyes), and his body is the same pink colour as Steven's during his breakdown.
- Non-Malicious Monster: It's easy to see from his expressions that he's mostly confused and angry, never directly attacking anyone, just destroying the scenery and unleashing a defensive shockwave, and not resisting when his family comes to give him a Cooldown Hug.
- No-Sell: The Diamonds use of their abilities to help Steven end up being nullified, even White Diamond was unable to reach Steven with her powers.
- Not Zilla: Some traits on his design resemble Godzilla, both being long-necked reptilian humanoids created by negative human actions, in this case internal turmoil rather than nuclear weapons. His spikes even glow just before he unleashes his power.
- The One Guy: He's the only male Gem Monster.
- Superpowered Evil Side: The creature is a culmination of Steven's guilt and trauma, seeing himself as an irredeemable monster after shattering Jasper and attempting to shatter White Diamond, and he's so powerful and unstoppable that not even the Cluster or the Diamonds themselves are able to stop his rampage, at least alone.
- Talking the Monster to Death: The Crystal Gems restore Steven by reassuring him that everything will be okay, and his family and friends are there for him even at his lowest points.
- Tragic Monster: He's the result of Steven having, in his own words after the fact, a big meltdown. He's brought back to normal once everyone brings themselves together to shower him with love and assurance.
- Walking Spoiler: It comes with being the territory of being Steven's form of self-anger and own thoughts of being a monster.
- Woobie, Destroyer of Worlds: Steven becomes this thing when his trauma and pain finally overflow and explode, causing him to turn himself into a rampaging monster.
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.
- One-Shot Character: Each Gem Cluster has one appearance each.
- 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.
- Out of Focus: They become scarce rather quickly after the Cluster issue is resolved, only appearing a few time among Jasper's captured corrupted gems and receiving a few mentions. They don't get any significant mention until "Homeworld Bound", when we find out Yellow Diamond is repairing them.
- 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.
- Undeath Always Ends: Future reveals that, with careful separation and repair plus Yellow Diamond's powers, they can be restored to almost the same as before they were shattered. Yellow Diamond fully plans to fix every cluster gem, even the Cluster itself, though it will obviously take a long time.
- Vagina Dentata: The large red cluster in the Kindergarten has a vertical fanged mouth which greatly resembles a vagina. Inside the mouth is 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.
- Arc Villain: For the second season and the opening episodes of the third. The Cluster itself isn't villainous at all, but stopping its formation drove the overarching plot of the second season.
- Astonishingly Appropriate Appearance: Its arm form is made of layers of stratum that greatly resemble the musculature of a human arm.
- Back for the Finale: It returned in "I Am My Monster" to try to hold Corrupted Steven back, and afterwards, hold his hand.
- 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.
- Done again in "I'm My Monster". When a crazed Monster Steven is about to charge at his friends, the Cluster once again manifests themselves as an arm to hold Steven back, giving his friends some valuable time to figure out how to bring him back to normal.
- 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.
- Earn Your Happy Ending: After thousands of years of torment for not being able to feel whole, the gemshards in the Cluster finally find a stable form where they achieve their wholeness through the company and comfort of each other, thanks to Steven teaching them how to bubble themselves. Furthermore, In Steven Universe Future, Yellow Diamond finds an effective way to reconstruct shattered gems and reveals her intention to heal all the gemshards inside the Cluster, meaning that eventually all of them will have a normal life again.
- 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.
- Godzilla Threshold: The only times it has emerged have been to help the heroes against literally Kaiju-sized threats: the Diamonds in their giant spaceships and Monster Steven.
- 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.
- Hoist by Their Own Petard: The Homeworld Gems created this thing with the intent on using it as a planet-destroying time bomb, but when their leaders attack and awaken it with the intent of annihilating Earth, the splintered minds within have other ideas.
- 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. However, in "Reunited", Steven just calls it "Cluster" as if it was a name.
- 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.
- Undead Abomination: To an even greater degree than the other Cluster Gems. Its horrifically powerful, being able to fend off Yellow Diamonds ship by just forming a hand, has a collective mind so overwhelming that it made Steven beg the Cluster to stop after just talking to him, and its physical form is positively titanic. Even when it merely manifested an arm, the appendage by itself was miles long, and its implied that the whole creature would be planet-sized, or bigger.
- Undeath Is Cheap: In Future, Yellow Diamond is able to repair shattered gems shards, and fully plans to restore the entire Cluster. Obviously, this will take an extremely long time, and hasn't happened by series' end.
- 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.
- The Worf Effect: Even it can't hold Corrupted Steven back for long, though its intervention still bought the heroes critical time while they were overwhelmed.