Bog Worms are flying, leech-like inhabitants of grim swamps. In cold regions they are sometimes called "Fen Wurms."

Their attack can be terrifying, springing from muck puddles and ponds in the fens of the Mist Swamps, propelled by their powerful, rubbery wings. When they strike, they latch on with their stinging tentacles and attempt to paralyse prey. If the prey is small, they will carry it away with them; if larger, they will attempt multiple attacks.