Bonedrinker

Keen Smell. The bonedrinker has advantage on Wisdom (Perception) checks that rely on smell

Undead Fortitude. If damage reduces the bonedrinker to 0 hit points, it must make a constitution saving throw with a DC of 5+ the damage taken, unless the damage is radiant or from a critical hit. On a success, the bonedrinker drops to 1 hit point instead. 

Spider Climb. the bonedrinker can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check. 

Multiattack. The bonedrinker makes three attacks: 2 with its claws and one with its tentacles, if the bonedrinker has a target grappled it can substitute a bonedrink attack with the tentacle attack. 

Claw. Melee weapon attack: +4 to hit, reach 5ft., one target. Hit: 6 (1d8+2) slashing damage 

Tentacle. Melee weapon attack: +4 to hit, reach 5ft., one target. Hit: 9 (2d6+2) bludgeoning damage, and the target must make a DC 12 Strength check or be grappled by the bonedrinker. If the bonedrinker has a target grappled it cannot attack with its tentacles. 

Bonedrink. If the bonedrinker has a target grappled with its tentacles, the bonedrinker can use this attack on them. The creature must make a DC 15 Constitution check or take 11 (2d10) necrotic damage from which the bonedrinker heals as much as the damage.