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Question though, isn't simeon a Luke card?
I'm inclined to agree with yirgogo. The exchange cannot be undone, but the band can be. I know that I would have ruled that Moses goes back to wherever the angel came from, and Simeon would be alone in a FBTN battle (except that Judges cards would be CBN). There is no "indirect" negation of the exchange, since the angel stays wherever Moses came from (hand, territory, deck or discard pile).
Than if an Angel was getting discarded during battle, could you play Swift Beings, and than Wings to exchange the angels and protect the rescue attempt from failing?
In addition to switching locations, if either of the cards is targeted by other abilities when the exchange is carried out, the targets of those other abilities are also switched.
I know I'm.a.little late but the reason I asked with AWTSN is a prophet I didn't think auto was.
Okay, that makes sense, I believe that the card I was thinking of was an Angel Wars card, Silver Enhancement: Exchange this hero with a hero in territory or in Chamber of Angels.