Mind Flayer
Medium-Size Aberration
Hit Dice: 8d8+8 (44 hp)
Initiative: +6 (+2 Dex, +4 Improved Initiative)
Speed: 30 ft.
AC: 15 (+2 Dex, +3 natural)
Attacks: 4 tentacles +8 melee
Damage: Tentacle 1d4+1
Face/Reach: 5 ft. by 5 ft./5 ft.
Special Attacks: Mind blast, psionics, improved grab, extract
Special Qualities: PR 25, telepathy
Saves: Fort +3, Ref +4, Will +9
Abilities: Str 12, Dex 14, Con 12, Int 19, Wis 17, Cha 17
Skills: Bluff +8, Concentration +12, Hide +8, Intimidate +10, Knowledge (any two) +9, Listen +10, Move Silently +7, Spot +10
Feats: Alertness, Combat Manifestation, Dodge, Improved Initiative, 
Weapon Finesse (tentacle)
Climate/Terrain: Any underground
Organization: Solitary, pair, inquisition (3-5), or cult (3-5 plus 6-10 grimlocks)
Challenge Rating: 8
Treasure: Double standard
Alignment: Usually lawful evil
Advancement: By character class; a mind flayer's favored class is psion
Mind flayers speak Undercommon but prefer to communicate telepathically.
Combat
Mind flayers like to fight from a distance, using their psionic abilities, particularly their mind blast. If pressed into melee combat, a mind flayer lashes its enemies with the tentacles ringing its mouth.
Psionics (Sp): At will: astral projection (11), charm monster (6), detect thoughts (5), levitate (4), plane shift (9), and suggestion (5). These abilities are as the powers manifested by an 18th-level psion (save DC 1d20 + parenthetical number).
Psionic Attack Modes (Sp): At will: Ego Whip, Mind Blast, Mind Thrust
Psionic Defense Modes (Sp): At will: Empty Mind, Intellect Fortress, Mental Barrier
Telepathy (Su): Mind flayers can communicate telepathically with any creature within 100 feet that has a language.
Improved Grab (Ex): To use this ability, the mind flayer must hit a Small to Large creature with its tentacle attack. If it gets a hold, it attaches the tentacle to the opponent’s head. A mind flayer can grab a Huge or larger creature, but only if it can somehow reach the foe’s head. After a successful grab, the mind flayer can try to attach its remaining tentacles with a single grapple check. The opponent can escape with a single successful grapple check or Escape Artist check, but the mind flayer gets a +2 circumstance bonus for every tentacle that was attached at the beginning of the opponent’s turn.
Extract (Ex): A mind flayer that begins its turn with all four tentacles attached and successfully maintains its hold automatically extracts the opponent’s brain, instantly killing that creature.