Undead Troll

Keen Smell:The troll has advantage on Wisdom (Perception) checks that rely on smell.

Regeneration:The troll regains 10 hit points at the start of its turn. If the troll takes acid,fire or Radiant 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.

Variant: Loathsome Limbs Whenever the troll takes at least 15 slashing damage at one time, roll a d20 to determine what else happens to it: 1-10: Nothing else happens. 11-14: One leg is severed from the troll if it has any legs left. 15- 18: One arm is severed from the troll if it has any arms left.
If the troll loses and arm it loses one of its claw attacks, if loses Both arms it loses both claw attacks.
On a successful D20 of a DC12 the Troll regenerates one of its limbs. regaining an arm it regains that attack.

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

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

Claw: Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage.