How plague used to work (not how it works anymore)
Plague's Trance: Swarm Form
"This vile spell is a recent innovation in magic, but its use has already been prohibited by four of the Nine Nations."
Upon use, releases a swarm of flies in front of the player. The flies will home in on enemies, dealing minor amounts of damage while inflicting poison and blight. Blighted enemies' corpses will explode into more flies after 15-30 seconds.
Trance: Swarm Form. The player turns into a swarm of flies. These flies poison enemies on contact. Grants the power of flight for the duration of the trance, which is 2 seconds. Afterwards, for a short time, pressing jump will allow the player to re-enter swarm form.
Overload: Unknown.
Unstable version: Plague flies come out of your back and front. Instead of just the front.
Will also poison a nearby area of water.