Arksiane WrathCannon is a ranged Weapon which deals 36 damage (x18). It belongs to the Vethean Weapons. Arksiane WrathCannon needs ammo, which is currently unknown. The infotext says that the ammo is "Arksiane WrathCannon", which is a bug.
You can get it, by putting a Cannon Template with 31 Arksiane Lumps in a Infusion Table which are generated in Vethea.