A troll blasted with psychic energy can take a non physical form upon regenerating. The troll’s psyche survives, but the body is as insubstantial as shadow.
The troll might be unaware of the transition the creature still moves and attacks with teeth and claws as ever but now the troll strikes at victims’ minds.
Monster: Spirit Troll (5e)
Large Giant, Typically Chaotic Evil
Proficiency Bonus: +4
Armor Class: 17 (Natural Armor)
Hit Points: 130 (20d10 + 20)
Speed: 30 ft.
STR – 1 (-5) • DEX – 17 (+3) • CON – 13 (+1) • INT – 8 (-1) • WIS – 9 (-1) • CHA – 16 (+3)
Skills: Perception +3
Damage Resistances: acid, cold, fire; bludgeoning, piercing, and slashing from nonmagical attacks
Condition Immunities: exhaustion, grappled, paralyzed, petrified, prone, restrained, unconscious
Senses: darkvision 60 ft., passive Perception 13
Challenge: 11 (7,200 XP)
Incorporeal Movement: The troll can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.
Regeneration: The troll regains 10 hit points at the start of its turn. If the troll takes psychic or force damage, this trait doesn’t function at the start of the troll’s next turn.
The troll dies only if it starts its turn with 0 hit points and doesn’t regenerate.
Multiattack: The troll makes one Bite attack and two Claw attacks.
Bite: Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 19 (3d10 + 3) psychic damage, and the target must succeed on a DC 15 Wisdom saving throw or be stunned for 1 minute.
The stunned target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
Claw: Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 19 (3d10 + 3) psychic damage.