Echolocation. The hook horror can’t use its blindsight while deafened.

Keen Hearing. The hook horror has advantage on Wisdom (Perception) checks that rely on hearing.

Mind Flayer Host . Voidmind hook horrors are all bonded to an Ulitharid. The Ulitaharid is instantly aware if any one of them is harmed or becomes the target of any magic. The Ulitharid can also see and hear through the eyes and ears of a voidmind hook horror as a standard action to a range of 5 miles. Maintaining this link requires concentration, but the Ulitharid remains aware of its own surroundings and can move normally. At will, the Ulitharid can take control of a voidmind hook horror, as if using the dominate monster spell (no save). While in control, the Ulitharid can manifest its spell-like abilities through the voidmind hook horror, as though it were manifesting the ability itself.

Sentient Tentacle. A voidmind hook horror’s tentacle can attack of its own accord as a free action once per round.

Multiattack. The hook horror makes two hook attacks.

Hook. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 11 (2d6 + 4) piercing damage.

Tentacle. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 11 (1d8 + 6) bludgeoning damage.

Rending Bite. A voidmind hook horror automatically hits with its bite if it grapples a foe, dealing 3d6+13 points of damage.

Cone of Slime. Once per day, a voidmind hook horror can spew psionically charged slime from its head in a 30-foot cone. Every creature in the area takes (8d6) acid damage (DEX DC 16 half) and be stunned for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Mind Blast (Recharge 5–6). The mind flayer magically emits psychic energy in a 60-foot cone. Each creature in that area must succeed on a DC 15 Intelligence saving throw or take 22 (4d8 + 4) psychic damage and be stunned for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Constrict. A voidmind hook horror deals 1d8+10 points of damage with a successful grapple check, in addition to damage from its tentacle attack.