Remission. If the abomination is in its humanoid form and takes no actions, it regains 1d6 + 4 hit points at the end of its turn. 

Shapechanger. The abomination can use its action to polymorph into a monstrosity-humanoid hybrid, or back into its true form, which is humanoid. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Multiattack. The abomination uses beast's bile (if available) and makes two attacks, one with its bite and one with its claws or chains.

Bite (Humanoid or Beast Form). Melee Weapon Attack: +7 to hit, reach 5 ft., 1 target. Hit: 10 (1d6 + 5) bludgeoning damage. 

Chains (Humanoid Form Only). Melee Weapon Attack: +7 to hit, reach 10 ft., 1 target. Hit: 8 (1d4 + 5) bludgeoning damage. 

Claws (Beast Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., 1 target. Hit: 12 (2d6 + 5) bludgeoning damage. 

Beast's Bile (Recharge 5-6). The abomination spits a poisonous liquid in a 10 ft. cone. Any creature caught in the area must make a DC 14 Constitution saving throw, taking 1d10 poison damage on a failed save, or half as much on a successful one. 

Instant Remission. If the abomination starts its turn within 30 ft. of a silver holy symbol while in beast form, it must immediately use its reaction to revert to its humanoid form. It then regains 1d6 + 4 hit points and ends its turn.