Just played a game against an opponent who kept playing Demonic Pacts to delay losing the game. They would get the benefit from one and then play another. When upkeep came around, they were able to choose ONE effect (any that were still available on a single card) and that was it.

This allowed them to Chose Damage/gain twice and it only progressed each card once. This effectively let them gain the benefits of Demonic Pact and delay the "lose the game" clause for two turns for every new Pact they played