Leeches

Leeches are minor antagonists in Little Nightmares who appear in The Prison and the Depths/Sewer.

Appearance
The Leeches are long, black, slimy snake-like creatures. They have no discernible face, just a sharp-toothed mouth on one end. They are shown to have two pair of legs, but have no use for them.

Summary
The Leeches are the first enemy encountered by Six in The Maw, found in dark places in The Prison. If they so much as touch Six, they will drain her blood in a matter of seconds due to their large size, instantly killing her. Six can also kill Leeches by throwing heavy objects at them, when a leech is killed this way, it will shrivel up and doesn't move or attack. Avoiding them is easy, if you're quick and cautious. Some can be found hanging above, some are already on the ground, ready to kill the player, so an awareness of surroundings and Six's lighter are necessary tools to stay alive. The Leeches live in the water. In the Secrets of the Maw, they attack the Runaway Kid. One Leech can be found under a bed the Runaway Kid jumps on. In the Sewer, a Leech has (apparently) killed the Runaway Girl, though there is a possibility she escaped and was killed by the Granny. They later attack the Runaway Kid in an area with shallow water, in which they move faster.Later a cluster of them is found on a hole where he must remove them to go through. One Leech is the unwilling guardian for the key of the Granny.

Possible Theories
It has been speculated that The Leeches are the remains of The Guests

Official Summary
Bloodsuckers

In the dark, moist corners of The Maw, the leeches writhe as one, awaiting the swollen wanderers. Slimy, venomous parasites that feed on the living – the leeches truly belong here.

Strategy
While leeches can be killed during gameplay (the player can throw a heavy object at a leech, when it shrivels up, it no longer moves or attacks), their numbers are much too high and there are few objects to use in the first place, so avoidance is the best option. Most leeches will be hidden beneath objects or in the darkness, but blood smears or pools are a clear sign to their location, so keep the lighter on hand. Leeches move quite slowly, so if stuck in an encounter with them, sprint towards the nearest exit.