Black dog

Messenger of the fay

When the black dog moves roll a d6 on a 5-6 the black dog teleports to the faywild or the material plane it can return to its original plane on a 5-6 if the black dog is hit with a cold iorn weapon it loses this ability permanently 

Soul render  if a black dog kills a creature the black dog can drag the corps to the faywild

Keen Hearing and Smell. The wolf has advantage on Wisdom (Perception) checks that rely on hearing or smell.

Pack Tactics. The wolf has advantage on attack rolls against a creature if at least one of the wolf's allies is within 5 feet of the creature and the ally isn't incapacitated

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 7 (2d4 + 2) piercing damage. If the target is a creature, it must succeed on a DC 10 Charisma saving throw on a fail the target is knocked prone