The Sundering: Rise of the Witch King is a mod for Medieval 2: Kingdoms and based around the fantasy world of Game workshop's Warhammer universe during the civil war between the Elves, the mod's campaign opens with the Death of Bel Shanaar in -2751 IC.
The Imperial Gunnery School at Nuln is the biggest cannon foundry in the world. It is here where the Great Cannons of the Empire are made. Mortars are shorter, heavier weapons than cannons, designed to lob an explosive shell high into the air so that it drops down onto the target.
Looks devastating,nice model.
I guess it fires octagon shaped shells. :D