Vailing

Darkvision: The Vailing has darkvision up to 120ft.

Latch on: after a successful bite attack latches onto the target. DC 18 Strength check   to break out of it. If the Vailing is Latched on the target at the beginning of its turn deals (3d) necrotic damage

If the Vailing takes any damage while latched on to a target it takes half damage  as well as the target taking the other half.

Multiattack. The Vailing makes two attacks: one with its bite and one with its tail.

Bite. Melee Weapon Attack: +9 piercing damage plus 10 (3d6) necrotic damage. 

Tail. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 14 (2d6 + 4) slashing damage, and the target is poisoned (Constitution save DC 14). for 1 minute.