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Gain control of all creatures target opponent controls until end of turn. Untap those creatures. They gain haste until end of turn. You can't attack that player this turn. You can't sacrifice those creatures this turn.
If an effect instructs you to sacrifice a creature, and you control any creatures other than the ones you gained control of with Call for Aid this turn, you must sacrifice one of them. You can't try to sacrifice one of the creatures you gained control of, fail, and therefore ignore the effect.
You can't sacrifice the creatures you gained control of with Call for Aid this turn for any reason. If an effect instructs you to sacrifice one of them, you can't and it remains on the battlefield. You also can't sacrifice any of them to pay a cost that requires you to sacrifice a creature.
