Innate Spellcasting (Psionics). The yangethe’s innate spellcasting ability is Intelligence (spell save DC 15). It can innately cast the following spells, requiring no components:
False Appearance. While the yangethe remains motionless, it is indistinguishable from a normal tree.
Magic Resistance. The mind flayer has advantage on saving throws against spells and other magical effects.
Multiattack. The yangethe makes two slam attacks. Tentacles. Melee Weapon Attack: +10 to hit 1d20+10 , reach 15 ft., one creature. Hit: 15 (2d10 + 4) 2d10+4 piercing damage. If the target is Large or smaller, it is grappled (escape DC 15) Feeding Tentacles. Melee Weapon Attack: +10 to hit 1d20+10 , reach 5 ft., one humanoid grappled by the yangethe. Hit: The feeding tentacles siphon away the victim’s emotions and deals 1 level of exhaustion. The yangethe heals 10 points of damage for each level of exhaustion it inflicts in this manner. As long as a creature continues to suffer this drain, each time it attempts to sleep it is affected by a nightmare spell, experiencing terrifying dreams in which it relives the feeling of being fed upon over and over. Psychic Blast (Recharge 5-6). The yangethe psioncily manifests psychic energy in a 60-foot cone. Each non-yangethe in that area must succeed on a DC 15 Intelligence saving throw or take 22 (4d8 + 4) 4d8+4 psychic damage and be confused 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. If a creature is reduced to zero hit-points by this attack they fall asleep and cannot wake until they heal of any exhaustion drain and have a hit point total above 0.
This six-eyed horror looks something like a dead tree with claws, tentacles, spidery legs, and a mouth bulging with tentacles.