Final answer:
The item in 'The Binding of Isaac' that heals the player and hunts enemies is the Leech.
Step-by-step explanation:
The item in The Binding of Isaac that spawns a creature which hunts down enemies, heals the player for half a heart upon consuming an enemy, and deals 1.5 contact damage per tick is the Leech. The Leech will actively pursue enemies throughout the room and, once it makes contact with an enemy, it attaches to them and damages them until they are defeated. After consuming an enemy, it provides the healing benefit to the player, making it a useful familiar for both offense and sustain.