MTGNexus

Cards in question:

The following scenario happened the other night in a game, and I wasn't sure how it was supposed to shake out.

I have Double Vision on the field. I was attacked by a creature with double strike. I cast Deflecting Palm. Now, since Deflecting Palm will be copied by Double Vision, what exactly happens? What I think will happen (and how we played it) is as follows. Both Deflecting Palms try to prevent the first instance of damage. One succeeds and will deal said damage back to its controller. The second doesn't actually end up preventing anything, as it's already been prevented, and does nothing.

I'd like the second Palm to prevent the second instance of damage from the double strike, but I don't think it will.

You get to prevent both instances of damage.

Both palms have resolved, and you are being dealt first strike damage. Both palms say "Hey, I would like to prevent that damage" as the affected player you choose the order for replacement effects, let's assume there aren't any other ones. You apply one palm now you have 0 damage being dealt the other plan goes "oops, my bad, nothing for me to do here I'll keep waiting for my turn"

Later in the turn, you are dealt normal combat damage. The prevention shield from palm says "Hey, I would like to prevent that damage" with no other replacement effects available it stops the damage.

This works because 0 damage being dealt is considered as damage isn't being dealt so you can't use up both shields on one instance of damage.

Assume you chose the attacking creature as the source of damage for both Deflecting Palms. The next time the attacking creature would deal damage (not just combat damage) to you this turn, there will be two effects that affect the damage that would be dealt to you, here, two Deflecting Palms, so you choose one of them, the damage is prevented, and the chosen Deflecting Palm deals damage to the source's controller. Now the other Deflecting Palm won't apply anymore, since it's not the attacking creature that would deal the damage, but the first Deflecting Palm, so the other Deflecting Palm waits until the next time the attacking creature would deal damage to you this turn.

EDIT (Feb. 3): Correctness edit.

Thank you @user_938036 and @peteroupc. I appreciate the help!