Contagion
The Contagion is a Daemon Engine of Nurgle and is an over glorified trebuchet. Like the Squig Catapult, it seems that in the grimdarkness of the 41st millennium, catapults still find some usage from the forces of Chaos.
The Contagion's main weaponry is the trebuchet which flings diseased shit/dead people/used up adult diapers/your sister's tampons/vomit/more shit at their enemies. While highly inaccurate being a trebuchet from the medieval ages and all, the main job of the Contagion is less on a direct hit and more on the spread of Papa Nurgle's Christmas gifts. While the trebuchet is used for long ranges, at close range the Contagion is far from defenseless as it mounted a forward puss cannon which sprays a stream of highly infectious diseases and parasites.
To make matters worse, the Contagion is made up of wood...well....magic wood at least that has been blessed by Nurgle. What you literally think that Nurgle is stupid enough to send in normal wooden engines of war in an age of lasers and rockets? Anyway these blessed wood are as tough as ceramite and are known to deflect multiple Bolter shells and even Battlecannon shells.
The only downside of the Contagion is its slow as molasses speed and having no defenses if assaulted at the side or rear.