XENOS: YANGETHE

Valley of the Brain Collectors as a sandbox had plenty of optional encounters.  Here is one which my players missed.  Disgusting creature.  Original here. 

YANGETHE
Huge aberration, chaotic good

Armour Class 16 (natural armour)
Hit Points 138 (12d12 +60)
Speed 30 ft.

STR 23 (+6)        DEX 8 (-1)          CON 21 (+5)
INT 12 (+1)         WIS 16 (+3)        CHA 12 (+1)

Damage Resistances bludgeoning, piercing
Damage Immunities cold
Damage Vulnerabilities fire
Condition Immunities, fear, mind-affecting effects
Senses passive Perception 13
Languages Aklo; telepathy 60 ft.
Challenge 9 (5,000)

False Appearance. While the yangethe remains motionless, it is indistinguishable from a normal tree.

ACTIONS                              
Multiattack. The yangethe makes two slam attacks or two tentacle attacks so long as no target is grappled by the yangethe. It may also make a psychic blast attack when available.

Slam. Melee Weapon Attack: +10 to hit, reach 5 ft., one target.
Hit: 16 (3d6 + 6) bludgeoning damage.

Tentacles. Melee Weapon Attack: +10 to hit, reach 10 ft., one creature.
Hit: 15 (2dl0 + 4) piercing damage. If the target is Large or smaller, it is grappled (escape DC 15)

Feeding Tentacles. Melee Weapon Attack: +7 to hit, 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 5 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. All effects from the feeding tentacles are mind-affecting effects.

Psychic Blast (Recharge 5-6). The yangethe 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 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 are knocked out.

DESCRIPTION                    
This six-eyed horror looks something like a dead tree with claws, tentacles, spidery legs, and a mouth bulging with tentacles.