Quote from DeadseedI would recommend Hell's Caretaker with possibly Thornbite Staff. With a creature in your graveyard and another in play you can sac one to bring the other one back, then repeat over and over to pump Thraximundar up infinitely.
Quote from Kid IcarusSome cards off the top of my head:
Chainer, Dementia Master
Balthor the Defiled (Pumps up Chainer!)
Read the Runes (Fills your graveyard for Patriarch's Bidding/Oversold Cemetary/Balthor, plus it's just good at digging for answers or threats)
Also, Darksteel Ingot is strictly better than Obelisk of Grixis.