Mind flayer

Mind flayers, also known as illithids, are aberrations with potent psionic abilities, inhabiting the Underdark of Exandria.

Appearance
Mind flayers are characterized by their exceptional height for a humanoid, purplish skin, and facial tentacles, surrounding their toothy maw.

Abilities
The following is drawn from the Monster Manual, 5th Edition, pp. 221–222, and has been demonstrated onstream. While illithids do not typically possess arcane abilities, they are resistant against spells and magical effects and are able to cast Detect Thoughts, Levitate, Dominate Monster, and Plane Shift (only on themselves). Mind flayers have the abilities to invade and control creatures's mind.

They have several offensive moves at their disposal. Mind Blast, a magical surge of psychic energy in a 60-foot cone that deals psychic damage stuns anyone, who failed a DC 15 Intelligence, for 1 minute. Tentacles, dealing psychic damage and, if the creature is medium or smaller, grappling them. The creature also must succeed on an Intelligence saving throw (DC 15) or be stunned until the grapple ends. While illithid's target is grappled, illithid can attempt to extract their brain, dealing massive amounts of piercing damage. If the creature's HPs reduced to zero, the creature instantly dies, as its brain is removed and eaten.

Mind flayer arcanist
The mind flayer arcanists are a 1Oth-level spellcasters and have the following wizard spells prepared, using their Intelligence to cast them (save DC 15, +7 to hit with spell attacks):


 * Cantrips (at will): Blade Ward, Dancing Lights, Mage Hand, Shocking Grasp
 * 1st level (4 slots): Detect Magic, Disguise Self, Shield, Sleep
 * 2nd level (3 slots): Blur, Invisibility, Ray of Enfeeblement
 * 3rd level (3 slots): Clairvoyance, Lightning Bolt, Sending
 * 4th level (3 slots): Confusion, Hallucinatory Terrain
 * 5th level (2 slots): Telekinesis, Wall of Force

Society
Mind flayers build their communities around enslavement of other races and the mind-control. Each illithid is connected by a central intelligence, known as an elder brain, that telepathically projects its desires to the illithids within 5 miles.

Mind flayers are suspicious of the arcane, and practice of such considered to be evil and can lead to expulsion from their society. Clarota described illithid society as well-structured, with groups of mind flayers being broken into creeds, with each individual mind flayer supporting the whole.

Illithid rarely approach the surface, instead preferring to bring things to them and remaining unseen. Conquering a location isn't as important to them as building up a base of power and perhaps then jumping to a new plane or a new society.

There are several species, including the githyanki, across multitudes of planes that constantly hunt mind flayers in an attempt to eradicate them.

History
Mind flayers originated in the Far Realm.

Vox Machina encountered several mind flayers during their travels in the Underdark. They also infiltrated a mind flayer city of Yug'Voril and nearly destroyed the elder brain residing within.

In case, Kraghammer had become a big enough problem for illithids, they might have hollowed it out, destroyed the denizens and left the ruins as they were too close to the surface.

Known illithid

 * Clarota: A magic-wielding illithid and former ally and companion of Vox Machina, who was killed after betraying the group.

Trivia

 * Due to Mind Flayers being Product Identity of Wizards of the Coast under the Open Game License, they are referred to simply as "Flayers" in the Critical Role: Tal'Dorei Campaign Setting.