Scrag

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

Amphibious. The scrag can breathe both air and water.

Regeneration. The scrag regains 10 hit points at the start of its turn. If the scrag takes acid or fire damage, this trait doesnt function on its next turn. This trait also doesnt function if the troll hasnt been immersed in water since the start of its last turn. The troll dies only if it starts its turn with 0 hit points and doesnt regenerate.

Severed Limbs. If the troll is dealt a critical hit with a slashing weapon, one of its extremities is severed. The extremity has AC 15, 10 hit points, a Speed of 10, and the trolls Regeneration trait. The troll controls the severed extremity and perceives through it with the appropriate senses (for instance, it sees through the eyes of its severed head). As a bonus action, the troll can reattach the extremity. While the troll is missing the extremity, its maximum hit points are reduced by 10. Roll d6 to determine the severed extremity:

1-4: Arm. If the troll has an arm, it loses an arm. It loses one of its claw attacks, and the severed arm can make a claw attack.

5-6: Head. If the troll has a head, it loses its head. It loses its bite attack, and the severed head can make a bite attack.