Rot Troll

Large giant, Chaotic Evil

Armor Class 16 (natural armor)

Hit Points 138 (12d10 + 72)

Speed 30 ft.

STR 18 (+4)

DEX 13 (+1)

CON 22 (+6)

INT 5 (-3)

WIS 8 (-1)

CHA 4 (-3)

Skills Perception +3

Damage Immunities necrotic

Senses darkvision 60 ft., passive Perception 13

Languages Giant

Challenge 9

Rancid Degeneration. At the end of each of the troll's turns, each creature within 5 feet of it takes 11 (2d10) necrotic damage, unless the troll has taken acid or fire damage since the end of its last turn.

Actions

Multiattack. The troll makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 4) piercing damage plus 16 (3d10) necrotic damage.

Claws. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage plus 5 (1d10) necrotic damage.

Source

Mordenkainen's Tome of Foes, p. 244