Call to the Grave + Endless Whispers will stick around, although the Magus is pretty hot. I can see what's going on, keeping the creatures for yourself by Terminating/Bolting everyone else's. Unfortunately in multiplayer most opponents will just gang you and pass their creatures to each other, like what Bob and I were doing against your Zombies when you tried to pull that off. What you want to do is keep everyone sacrificing as much as possible while you ramp some big spell (take your pick on something nasty), and just let the whole grave/whispers combo sit there as your stall engine.