This came up in our last game, my gf had a crystal and was standing against the edge, 3 minions surrounding her.
She drew 3 damage cards and before resolving the first, dropped the crystal. Luckily it bounced against the wall and she got it back.
Now does she need to drop it again before resolving card 2 (and possibly before 3 again) or is it once before resolving them al?
If the damage is considered simultaneous, like when minions attack, you only drop it once. If the damage forced you into lava or a spike wall, though, you'd need to roll again.