Never A1. Sometimes you can just A3 and win, especially since A3 counts as Casting creatures and thus Summoning as well. Otherwise A2 for Summoning creatures and to make enough black for A3 and green for Gather the Pack. Overwrite the Priest if you are really low on life, perhaps, otherwise you will probably want to cast him again and just overwrite or refuse the Demon.

The single turn of damage from A2 is usually much less than the repeated damage from A1 Devils. A3 is usually a bad idea, because you should be able to kill most things before they kill you, but they might kill the opponent before you want them dead.

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