Blood troll

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

Regeneration. The troll regains 5 hit points at the start of its turn. If the troll takes acid, poison, or fire 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 two attacks: one with its bite and one with its claws.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 4) piercing damage Target must make a dc 15 con saving throw if the target fails the blood troll regains hit points equal to half the damage dealt.

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