Leeches are enemies which are commonly found in the Womb and sometimes solely in the Depths. They float around at random and charge at the player in a manner similar to Chargers. However, as opposed to them, they are flying, and thus will pass obstacles until they hit the other side of the wall; they also charge at a much faster pace.
They can be considered upgraded Chargers.
In Sheol, The Womb and rarely in The Depths, there is an upgraded kamikaze leech (unofficial name) that is black and has an eye instead of a mouth. This variation of a Leech will explode upon death - which will be caused on touch, so be sure to dodge them!
This version can sometimes be spawned by Mom's Heart. Two of them are spawned with The Fallen at the beginning of the fight with Satan, and two of them will get constantly respawned during the final phase against his feet.
The third counterpart added in Wrath of the Lamb, the Holy Leech (unofficial name) can be found very commonly in the Cathedral and slightly less common in Sheol, The Womb, or Utero. They are very rarely found in The Depths.
They have the same traits as the Kamikaze leech, however aside from their altered white appearance they always have an Eternal Fly circling around it, which can block the player's projectiles.
- If a leech charges at you while it's aligned with a door, it will go through it and off the screen, until it eventually reappears when its charge ends.