Flesh Frenzy. The Abhorwretch has advantage on melee attack rolls against any creature that doesn't have all its hit points.

Grasping Claws. The Abhorwretch has five claws. Each claw can be attacked (AC 20; 10 hit points; immunity to poison, psychic and necrotic damage.) Destroying a claw deals no damage to the Abhorwretch, which can regenerate one replacement claw on its next turn. A claw can also be broken if a creature takes an action and succeeds on a DC 16 Strength check against it.

Rapid Regeneration. The Abhorwretch regains 30 hit points at the start of its turn. If the Abhorwretch takes radiant or lightning damage, this trait doesn't function at the start of the Abhorwretch's next turn. The Abhorwretch dies only if it starts its turn with 0 hit points and doesn't regenerate.

Undead Fortitude.  If damage reduces the Abhorwretch to 0 hitpoints, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or lightning. On a success, the Abhorwretch drops to 1 hit point instead.

Multiattack. The Abhorwretch makes 3 attacks with its claws, and two attacks with its bite.

Claws. Melee Weapon Attack: +8 to hit, reach 5ft., one target. Hit: 10 (2d6+3) slashing damage. The target is grappled (escape DC 16). Until this grapple ends, the creature is restrained, and the abhorwretch can't use the same claw on another target.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target the Abhorwretch has grappled. Hit: 14 (2d10+3) piercing damage, and 14 (4d6) poison damage.