If you don't reveal an Equipment card, or if the exchange can't be completed (such as if Arcanum Things is no longer on the battlefield, you don't own Arcanum Things, or the new Equipment can't be attached to the creature Arcanum Things is attached to), nothing happens
(If a permanent with a stun counter would become untapped, remove one from it instead.) If you choose the second mode, you don't have to choose which of the target creatures you'll put a stun counter on until Aerith Rescue Mission is resolving
I tried to ensure none of these would just ruin any of those formats
Sire of Seven Deaths This seven-costed, colorless seven in the name, seven keywords and 7/7 size is next
Yuffie enters attacking the same player, planeswalker, or battle the returned creature was attacking
When this iteration of Sisu comes into play, you get to banish all your opponent's characters with two strength or less