Well you can use butcher of Malakir (it has a built in grave pact) and use that with a sacrifice engine like vampire aristocrat or there's a new one in rise of eldrazi as well, to sacrifice weenie vamps like gul-draz or blood seeker or even bloodghast, which then makes your opponent sacrifice their creatures. If you use bloodghast, it will keep coming back everytime you play a land. I have a vamp deck and that usually works as a slow down or even a complete stop of opponents offense. Plus with It that Betrays you'll gain control of more creatures, a little faster
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Also, Glimpse the Unthinkable, mill 10 cards for a U and a B.