I really liked the fleshbag in the deck before and was always on the verge of playiing magus of the abyss just to have another copy. I really like having two sac outlet creatures at 3 mana.
@PtaQ : I can't see why you would want to play a card that is not a creature nor a card that interacts with them with this general. Our general provides both card advantage and inevitability, and while I don't see (yet) beastmaster as an obvious inclusion, I have long ruled the phyrexian arena out with the deck. Lyserg is a seasoned player with the deck and I am not taking his advice lightly
However I have noticed a CA enabler that might fit into our deck :
Qarsi High Priest
It would fill our grave while putting creatures on the battlefield, and provide us with a sac enabler, all this for quite a cheap cost. I would definitely test him in my Karador.