If my opponent has Grave Pact in play and two of his creatures are killed, can I sacrifice Reassembling Skeleton, bring it back, and sacrifice it again to satisfy Grave Pact?
yes, each pact trigger act as a "layer" and resolves once at a time.
something like (remember magic is a LIFO:Last In First Out system)
-PACT A triggers
-PACT B triggers
-PACT B resolves, you sacrifice skeleton
-you "revive" skeleton.
-PACT A resolves, sacrifice same skeleton.
you CANT do this when the sacrifice effect is in the same card, like with Torment of Hailfire.
remember that you can always react between different cards/triggers. (exception being split second cards)
something like (remember magic is a LIFO:Last In First Out system)
-PACT A triggers
-PACT B triggers
-PACT B resolves, you sacrifice skeleton
-you "revive" skeleton.
-PACT A resolves, sacrifice same skeleton.
you CANT do this when the sacrifice effect is in the same card, like with Torment of Hailfire.
remember that you can always react between different cards/triggers. (exception being split second cards)