Mimic Voice. This monster knows who you know closest and care about the most easily, able to speak in any language that the other creature it is targeting knows. A creature must make a DC 10 Wisdom (Insight) check in order to know if the monster is not their friend. 

Deceptively Human. The monster can appear like an average humanoid creature while in dim light or darkness if the other creature doesn't have Darkvision. 

Sadistic Intent. The monster can use it's Bonus Action to force one creature that can see it to make a DC 13 Wisdom saving throw or be frightened until the end of their next turn. 

Festering Blow. Melee Weapon Attack: +6 to hit, reach 10 ft., 1 target. Hit: 2 (1d4) necrotic damage, and have their Hit Point maximum is decreased by 1 until they take a long rest or have a Remove Curse or Lesser Restoration cast on them.

The monster can take 1 legendary action, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The monster regains spent legendary actions at the start of its turn.

Festering Blow (Costs 1 Action). Your Friend can perform a Festering Blow.