Twin Universes

At the beginning of your upkeep, flip a coin and apply the following effect:
HEADS: Exile all creatures on the battlefield and then return all cards exiled with the Tails effect to the battlefield under their owner's control, they gain haste until end of turn.
TAILS: Exile all creatures on the battlefield and then return all cards exiled with the Heads effect to the battlefield under their owner's control, they gain haste until end of turn.