- The Inadequacy and other monsters fought during "Dream Mentor", all of which are embodiments of Cyrisus' negative emotions.
- The Spirit Beast is a monstrous ghostly thing that lives in a parallel spirit dimension where it feeds off the souls of ghosts who became trapped there (inflicting And I Must Scream on them). It was trying to break between dimensions into the world of the living so it would have more souls to feed off of. The player is completely unable to directly attack it. It is defeated only by the player weakening it through indirect methods and then empowering the ghosts it was feeding off to be strong enough to finish it. Unfortunately, because of the properties of the parallel spirit world it was killed in, it death resulted in the manifestation of a Corporeal Beast in the real world. Luckily, the Corporeal Beast can be harmed by normal attacks, so this is better than if the Spirit Beast had escaped, but it still is one of the most dangerous monsters in the whole game.
- Tolna was a boy who was imprisoned and mind raped by an unknown force for several years until he turned into a horrific three headed reality warping abomination who manifests bizarre Mooks based on his emotions, Anger, Fear, Confusion, and Despair.
- It has been hinted that the unknown force that tortured Tolna was the semi alive remains of the dead hydra god Loarnab.
- The Stalkers are a race of eldritch horrors. They all have unnaturally huge eyes and weird attacks, and their language is said to be harmful to humans that hear it. The strongest of them is known as World-gorger Shukarhazh.
- And it turns out, all of the Stalkers are part of a vast Hive Mind. They are the spawn of a being called The Father, a brain that grew from a moon in the same solar system as the planet where demons came from. The Father has an obsession with gathering knowledge and created the Stalkers to be its eyes.
- The inhabitants of the Abyss and the Infernal planes. The ones that players most commonly encounter look like typical demons but the rest are far more alien. The Abyss itself (which is the dimension that allows teleporting to work) may be one, because it looks like the insides of some huge fleshy monster full of teratomas. It has been implied that the part of the abyss we have so far seen is inside the remains of the gigantic Chthonian demon Hostilus; Chthonian demons have the ability to assimilate the essence of whatever they eat and grow bigger and more powerful.
- The weird looking Penance monsters from the Barbarian Assault minigame have been revealed to be the spawn of a very powerful Cthonian demon who entered Gielenor by eating the soul of a barbarian who dreamed about him and emerging from her corpse after she died.
- The monster from the Survival Horror inspired quest Broken Home, see the page image. It looks like a gigantic slug covered in eyes and mouths. It can shapeshift into anybody it has eaten, including ghosts, will One-Hit Kill you if it catches you, and it may or may not be responsible for some of the weird unexplained events in the quest. It was released from an ancient mental hospital after somebody Dug Too Deep. He is a cthonian demon who went insane with guilt after accidentally eating a human girl he was trying to befriend, and he actually is a decent person when he isn't crazy, subverting Always Chaotic Evil.
- The Pests are a Horde of Alien Locusts from another dimension called the void that all have very weird appearances.
- From the Heart of Stone quest, we have the Prehistoric Abyssal. This entity existed before the current multiverse, and told Old Mentor Xenia about what the Elder Gods do to their perfect worlds as part of their life style. The Abyssal's motives aren't fully known, but he deliberately manipulated Xenia into waking up the Elder Gods (she thought she was killing them).
- The elder gods are 5 extremely powerful beings who have Complete Immortality (except possibly if their rebirth process fails) and are powerful enough create to planets and life. They barely acknowledged that intelligent life exists and each one is a personification of different aspect of reality. 4 of them are currently sleeping on Gielinor and bad things will happen when they wake up. they will destroy the entire universe in order to feed off of it's life energy, except for the Abyss and Gielinor, which will become a Death World, and they have done this many times before. Mah, the fifth Elder God who was left behind on the Death World Freneskae due to being reborn defective, is so powerful despite being severely weakened and barely alive that Zaros, who is one of the most powerful young gods ever, immediately runs when she wakes up enraged, and it has been implied that contact with Mah is what drove Amascut insane.
- It has been revealed that there actually is a sixth elder god who may be even more eldritch than the rest. Zaros describes them as "five of form, and one of ... something else."
- Muspahs are bizarre monsters manifested from the Mah's dreams. They are what the Mahjarrat, a race of Humanoid Abominations also created by Mah, have nightmares about. Mah also created Seren (ironically, one of the nicest of the gods) and Zaros (the most alien of the young gods, who went on to create abominations of his own, known as the Nihils.). Mah created Zaros, Seren, and the mahjarrat to be her playthings.
- During the quest One of a Kind, you enter a dragonkin's mind and fight against the Echo of Jas, a personification of the curse that the elder god Jas placed on the dragonkin. The Echo of Jas's examine text says "This dark humanoid shape is your mind's attempt to make sense of the awesome manifestation of an Elder God."
- The dragonkin Tarshak undergoes a horrifying transformation into an abomination after another dragonkin uses an artifact of the elder gods to kill V by transferring his power into Tarshak. He becomes a hideous fleshy thing with too many limbs and some arthropod like features that the player is completely unable to damage until you crush him under a huge bane ore rock, and he still manages to be an extremely tough opponent even after this.
- Xau-Tak, an evil god who has not yet appeared in the game, is strongly implied to be an eldritch horror. Durring the final battle against Rabid Jack, the player is attacked by a giant hand coming through a portal that may belong to Xau-Tak, and seeing it causes the player character to be driven insane if they aren't drunk enough. And hints of Xau-Tak's influence have appeared in many quests even outside of the Pirate storyline.
- The Skeletal Horror, a mind controlling skull of an Animalistic Abomination, that forms a body for itself out of the bones of many different animals, is implied to be one of Xau-Tak's servants.
- The Grotesque is a hideous bloated white creature with too many arms that is spreading corruption in Lumbridge swamp. The wall beasts in the caves below the swamp are actually it's arms.
- Mother Mallum is the queen of a race of mind controlling sea slugs that the player faces in a quest series heavily inspired by the works of H. P. Lovecraft, although she ends up being defeated rather anticlimactically.
- Ripper demons are grotesque demons who, as the name implies, have long blade-like claws. One of them was a top assassin for Zamorak during the God Wars and was eventually crippled by Saint Elspeth. It's mangled body was buried under the Abbey of St. Elspeth Citharede until a Zarosian zealot hired a group of miners to excavate the body. When it was found, it twisted the bodies of the miners and the zealot into more ripper demons, who now infest the cave where they were found.
- The Chaos Elemental is a bizarre monster that looks like a one eyed demonic creature with a cloud of smoke in place of a lower body. It used to look like a smoke cloud with tentacles before a graphical update. It has special attacks that unequip the player's equipment and confuse the player by teleporting them, both of which no or almost no other monster in the game can do. Its normal attacks can inflict magic, ranged, or melee damage, even when not in melee range. It is also a Giant Space Flea from Nowhere because it is found on the surface of the deep wilderness instead of in a dungeon or during a quest or minigame, and the game gives almost no warning about it, so unprepared players may run into it by accident and get killed in seconds. Nothing is currently known about what it is or where it came from. It also used to give players clues about future updates to the game through the Fourth-Wall Mail Slot.
- The Chaos Elemental also has a Good Counterpart in the form of the Balance elemental. Although the Balance Elemental simply looks like an elemental made from all four elements, it is possibly even stranger than the chaos elemental. When the player character fights it, it speaks to the player character as though they were a close friend who had already died, making the encounter very unsettling. The Balance Elemental is also said to exist in multiple dimensions at once. It was later revealed that the Balance Elemental was created by Guthix fusing together four elemental druids and the previous World Guardian who exists outside of time.
- The god Guthix was originally depicted this way in the Canon Discontinuity God Letters, being far more alien in mentality than the gods Zamorak and Saradomin, and also being a shapeshifter whose preferred appearance was a tentacled skull and claiming that his true name was not pronounceable by humans. The game completely ignores this now although before he finally appeared in the quest "The World Wakes" he was sleeping and it was believed by many that if he were to ever be awakened the world would be destroyed and reset and the threat of waking up Guthix was used by Guthix's worshipers to deter people from starting large scale wars. "The World Wakes" subverted this by revealing that although he is an exceptionally powerful god, he not more eldritch that most, unlike some of the other gods on this list.
Eldritch Abomination / RuneScape