Zuggtmoy, the Lady of Rot and Decay (from D&D)

Also known as the Demon Queen of Fungi, or the Lady of Rot and Decay, Zuggtmoy was a demon lord. Her only desire was to infect living creatures with her spores, making them her mindless slaves and, eventually, into rotting and decomposing hosts for mushrooms, moulds and spores that she spawned (extracted from the Forgotten Realms Wiki).