Deformis was created by Obsidian during the war against the Six Kingdoms as a sort of pack horse/whipping boy. Deformis was always considered the servant of the "master" race even though he was one of them. Eventually he became fed up with this and became Kokura's assistant/guinepig for any new devices he had constructed. During the Overthrow of Miserix he became a pack horse again, however this time more appreciated.
Yes, he has a huge as chain gun.