Bloodbeast

Amorphous The bloodbeast can move through a space at least 1 inch wide without squeezing. 

Hybrid Nature The bloodbeast counts as both an abberation and humanoid, and can be effected by anything that would effect either type of creature. 

Made From Blood When a creature within 10ft of the bloodbeast is reduced to zero hit points, the bloodbeast regains hitpoints equal to twice the number of hit dice that creature had, if the creature had blood. 

Multiattack The bloodbeast makes four claw attacks.

Claw Melee Weapon Attack: +9 to hit, reach 5 ft., 1 target. Hit: 7 (1d6 + 3) slashing damage and the creature must succeed on a DC 12 constitution save or take 10 (2d8) necrotic damage and have it's hit points reduced by the same amount. On a successful save the creature takes half as much necrotic damage and doesn't have it's maximum HP reduced. 

Extract Blood (1/Day) The bloodbeast magically draws on the vitality of the creatures around it. Each creature of the bloodbeast's choice within 30ft must make a DC 15 Constitution saving throw or take 28 (7d6) necrotic damage and the bloodbeast regains up to half it's hit points. On a successful saving throw, the creature takes half as much damage. Any creature that has no blood is immune to this effect.