Slimy, segmented wormlike creatures which live in water

Giant leeches are slimy, segmented wormlike creatures which live in water. Salt or fresh, clean or stagnant, there are giant leech varieties for all wet environments. However, only a true leech expert can tell the various types apart. An average giant leech will be 4 to 6 feet long. Once a giant leech hits in combat, it attaches to the victim and sucks blood, causing an additional 1d6 damage each round until the victim or the leech is dead. There is no way to remove the leech other than to kill it.

Horrid, 3-4' long, slug-like creatures with sucker mouths. Lurk in swamps.

Giant leeches that inhabit warmer, fresh water

Giant leeches inhabit warmer, fresh water. If a giant leech successfully hits a character, it drains hp equal to its hit dice each round automatically thereafter (so a 4 HD leech drains 4hp per round). A character bitten by a giant leech must save vs poison or suffer a disease that will be fatal in 1d6 weeks.