Just picture it.  Let them go first, Your hand is:
Putrid Imp, 2X Dark Ritual, Exhume, Reanimate, Entomb, and a Swamp.
You draw It That Betrays.
Play Swamp, Rit, Rit (now have 5 mana), Imp, Entomb (find Pathrazer and throw him in the hole), Discard It That Betrays to give the imp flying, (Still have 3 mana left) Exhume It That Betrays, Reanimate Pathrazer.

2 Eldrazi Fatties on turn 1, total annihilator of 5, and you get everything they sac? GG