Leech

The Leech is a wormlike enemy spawned by the Wall of Flesh Boss. Multiple Leeches are released from the Wall's mouth, first in groups of 3-4. The groups grow larger and more frequent as the boss takes damage. The Wall of Flesh will eventually release them in a continuous stream.

Tips

 * In normal mode, they will always drop a Heart when they die, but in Expert mode, the chances of a Leech dropping a Heart get reduced to a fifth. Preparing a platform before the fight can help you collect their dropped hearts.