Aboleth are twenty-foot long fish-like creatures with potent psionic abilities. They are considered impossibly ancient, older than humanity itself, and in possession of horrible secrets about the early history of the world. In murky subterranean waters, they enslave entire cities, and turn them into mucous-covered, mindless servitors with the ability to breathe water.
Aboleth resemble immense fish for the most part. They have four tentacles near their head, which they use in combat, and to drag themselves along the ground when out of water. Their toothless maw is located on their underside, and they have three slit-like, red-purple eyes, placed vertically on their foreheads.
Aboleth mostly use slaves to fight for them. When pressed into actual conflict, they strike with their tentacles, and attack with their mental abilities, which focus on domination and enslavement.
The aboleth exude a slime that causes those touched by it to become able to breathe water, but unable to breathe air. In water, it is surrounded by a cloud of this slime. They use this slime to allow their servants to breathe underwater.
The tentacles of the aboleth cause the skin to turn into a transparent membrane and quickly dry out, damaging those who are not kept damp and cool.
Aboleth have a range of psionic powers, the most prominent of which is their ability to fully dominate and control other beings, which they use in combat, and to permanently enslave others.
Aboleth lurk in aquatic regions under ground.
Aboleth first appeared in David "Zeb" Cook's Dwellers of the Forbidden City. They received attention in Dungeon and Dragon magazines, and then appeared in 2e's second Monstrous Compendium (being reprinted in the Monstrous Manual). In 3e and 4e, aboleths make an appearance directly in the Monster Manual.