You can use them both in a 50 card deck since they have different Art and different brigades, but you can't have both of them in play at the same time, since they are he same unique character. It's just like Esau and Esau the Hunter in that respect.
Evil enhancements that depict Morg:
Blade of Death, Evil Arises, Gathering of Demons, Intent to Kill, Knocked to the Ground, Pushed Back, Sword of the Rebellion, Torment, and Wings of Calamity
Pushed Back is probably the only other useful card that Morg can recur (withdraws a hero, cannot be prevented by silver). Blade of Death, Sword of the Rebellion, and Knocked to the Ground discard good enhancements in play or battle, Evil Arises bands a demon into battle (could be useful I guess), Wings of Calamity could make Morg's ability CBN (w00t!) and stop him from being ignored by Three Nails, and Sword of the Rebellion.
If you want to really do this, I would suggest adding in Possessing Demon and playing with a blue offense. That's the most effective way to have your demons capture heroes.