Plague tank

The Forsaken plague tank (also called a plague vat) is a mobile device with tanks of sludge and two huge sprayers, used to spread the new plague in places like Halgrind.

They are called both "Plague Tanks" and "plague tanks of sludge" in the same quest, so 'tank' likely refers to a container and not a vehicle.

They may also be called Chemical Wagons.