RuneScape has so many enemies that only appear in one place that this page has to be restricted to mainly the ones that don't have any explanation or are especially memorable.
- Revenants used to be wandering enemies only found in the wilderness that were added to keep the wilderness dangerous when the ability to attack other players was removed. When the ability to attack players in the wilderness was restored, revenants were confined to a single room in a dungeon below the Wilderness. There are 14 different kinds of Revenants, and since all of them are crammed into one room, several of them only appear one at a time.
- The Rock Golem, the Tree Spirit, and the River Troll can only be found in the Enchanted Valley. These enemies used to appear as random events before random events were removed from the game. The only stag in the game is also found there too.
- There is only one Air Wizard, Water Wizard, Earth Wizard, and Fire Wizard in the game. They are found near Port Sarim.
- On the island of Entrana, there is a unique enemy called the Entranan Firebird. You have to kill it once during a quest to get a feather from it.
- There is a secret enemy called the Tormented Wraith that can only found by going through the invisible spirit realm portal in the Dark Warrior's Fortress. It might also count as a Optional Boss since you can only access it after completing a quest, but the game doesn't list it as a boss anywhere, and it is pretty weak and has no special abilities aside from being unable to be fought if you aren't dressed like a Black Knight. Another spirit realm portal in the Wilderness contains enemies called Ghostly Warriors that aren't found anywhere else.
- There is a single unique lion like monster on Karamja called the Shaikahan that is immune to all weapon damage except for specially poisoned spears, although due to a change in RuneScape 3's combat system, poisoned spears are no longer usable by players in that game (though they still are in the Spin-Off, Old School RuneScape). It is still killable in 3 using other items such as familiars however. It drops a unique item called Shaikahan bones, but nothing else.
- Bandos's Throne Room contains several statues, some of which can come to life for you to fight them. There is only one Ourg Statue that can come alive, and it is the strongest of all the statues.
- There is a unique enemy called Salarin the Twisted in Yanille Agility Dungeon. He is the only enemy in the game that drops the Sinister Key that opens a chest in the dungeon. Although there is only one of him and he has some unique traits, he isn't listed as a boss and isn't fought in a quest.
- The Ancient Cavern contains several unique enemies. These include: Angry Barbarian Spirit, Enraged Barbarian Spirit (two of them), Berserk Barbarian Spirit, Lost Barbarian, Confused Barbarian, Skeleton Brute, Skeleton Thug, and Skeleton Warlord (also two of them). Rummaging a skeleton in the cavern may also spawn a skeleton heavy or a skeleton hero. It also is the only place where you can find Brutal Green Dragons, and it used to be the only place where you could find Mithril Dragons and Waterfiends.
- Early in RuneScape there was a single orc in the Tree Gnome Village hedge maze, which was the only orc in the game until it was removed. Later, when different orcs were later added to the game, they changed the spelling to "ork".
- There is a unique cyclops in a cage in Ardounge Zoo that is different than any other cyclops in the game, and it used to be the only cyclops in the game.
- When killing certain enemies in the game, there is a possibility of an elite version of that enemy spawning. These elite monsters are larger, have higher stats and better drops, and sometimes have special attacks that the regular enemies do not. For Rune Dragons, there is a very small possibility of a an Elite Rune Dragon spawning with the name "Barry the Destroyer". Barry the Destroyer is the same the regular Elite Rune Dragon, except it always drops the extremely rare Kethsi outfit scroll. Barry the Destroyer is an Ascended Meme, it is the name players gave to an Elite Rune Dragon that killed 32 players on the day Rune Dragons were first added to the game. When fighting Soulgazers, there is a very rare chance of spawning a special Soulgazer that is even tougher than the Elite Soulgazer called Veil-ripper Ozharakha, who always drops the extremely rare Hexhunter Bow.
- When fighting the Penance King, there is a very small possibility that a King Spawn named "Ospawn" will appear. This is a reference to a joke one of the developers made on Twitter.
- Although the Chaos Elemental counts as a boss, it behaves more like a common, though very powerful, enemy that there just happens to be only one of. It is the only non-quest boss in the game that doesn't have a lair it is confined to, instead it wanders out in the open near the Rouge's Castle in the Wilderness, and it spawns there just like a regular enemy, so if you don't know it is there you are likely to run into it by accident when exploring the Wilderness.
- Taverley Dungeon used to have a pair of suits of armor that would come to life and attack you if you tried to open the western gate of the room containing the cauldron of thunder but they have since been removed.
- Cockatrices and Aquanites are only found in the Fremennik Slayer Dungeon, which is just a long cave with a different kind of monster in each room of the cave, with no explanation of what any of the monsters are doing there. Several of the other monsters in the Dungeon also used to be only found there before they were added to other dungeons.
- Lumbridge Catacombs contains several kinds of monsters that are only found there. These enemies include warped animals and several unique kinds of undead.
- During the Temple Trecking / Burgh de Rott Ramble minigame, where players escorts adventurers and refugees through Morytania, the player may be attacked by several kinds of enemies that only appear during this minigame that you can't encounter when exploring Morytania alone. These unique enemies include Swamp Snakes, Giant Snails, Nail Beasts, Undead Lumberjacks, and a Swamp Creature, and all of these enemies except the Swamp Creature have unique drops. You can also be attacked by Ghasts that are stronger than the ones you normally encounter.
- Flesh crawlers, Catablpons, and a unique type of Shade are only found in the Stronghold of Security. The shades used to be a random event enemy that was removed. The Stronghold of Security also used to be the only place where you could find Minotaurs and Ankous before they were added to other places in the game.
- Zombie Rats are only found in Melzar's Maze
- Skeletal Wyverns and living Wyverns are only found in the Asgarnian Ice Dungeon
- Terror Dogs are only found at the end of Tarn's Lair, or when redoing the boss fight against Tarn in the Dominion Tower.
- Earth Warriors used to only be found in the Edgeville Dungeon, in a section that counts as part of the Wilderness.
- Rock Lobsters, Wallasalkis, and Spinolyps and most types of Dagannoth are only found in Waterbirth Island Dungeon. Dagannoth Fledglings, which strangely look different than normal Dagannoths or Dagannoth Spawn, are only found in a single room in the dungeon. The player isn't supposed to fight them, as they don't drop anything but bones and don't give Slayer experience when killed. They are there for an NPC to fight. Dagannoth Guardians are only found in their own dungeon also on Waterbirth Islands separate from the main one.
- Suqahs are only found on Lunar Isle
- Shadow Warriors are only found in the Legends' Guild Basement
- Otherworldly Beings, Mutated Zygomites, and baby Tanglefoots are only found on Zanaris.
- Molanisks are only found in the Dorgesh-Kaan South Dungeon
- Spectral attendants, Spectral tenders, Spectral cultivators, and Corruption beasts can only be found in the temple beneath Soul Wars, which can only be accessed during a quest.
- Large Mosquitos, Mosquito Swarms, Bush Snakes, and Broodoo Victims can only be encountered while doing the Tai Bwo Wannai Cleanup activity.
- The island of Mos Le'Harmless has several unique enemies. The surface of the island is the only place where Jungle Horrors, Giant Mosquitoes and a unique variety of poisonous Snake can be found. The dungeon beneath the island is the only place where Cave Horrors, Unspeakable Horrors, and Albino Bats are found.
- The Jade Vine Maze is the only place where you can find Tenacious Toucans, Pernicious Parrots, Giant Wasps, and poisonous Frogs. It also used to be the only place where you could find Giant Ant Workers and Giant And Soldiers, which are also found in the chaos tunnels.
- Death wings are only found in the Viyeldi caves explored during Legends' Quest, in a single room or spawning on rare occations when smashing barrels in another.
- Brine Rats are only found in a single room of the Brine Rat Cave. The cave is discovered during Olaf's Quest, but it isn't even required that the player enter the room where they are located to complete the quest.
- The chaos tunnels dungeon is notable for containing a random assortment of enemies that used to be unique to one location. For some of these enemies, this may have been done to give players an easier to reach place to fight them. Aside from the dungeon's boss and his minions, the only enemy it contains that is unique to it are the Dagon'hai monks.
