Leeches are ugly suckers. They’re water-bound monsters you’ll find exclusively in the Swamp. They apply a nasty Poison on-hit so it’s best to stay out of the water whenever possible.
Poison is very dangerous in Valheim and you’re extra vulnerable in the water. Leeches seem harmless until they surround you and you run out of stamina. It’s a quick trip to a watery grave.
Leeches can swim out to your Ship. You don’t want to disembark too early when entering a swamp.
The Hoe is the most powerful tool against leeches. You can raise ground in the swamp to make safe pathways through the otherwise dangerous wetlands.