The target of your rival's spell is no longer legal, so that spell is simply discarded to the graveyard
Other versions are still upwards of $20, making this a nice pickup thatll drop, but not by as much as youd like if youre wanting to grab a copy
For example, the activated ability of Aangs Iceberg requires that you waterbend 3, which means the player can tap artifacts and creatures to help pay the cost, or use old-fashioned mana to activate the abilities
Certainly, if you consider raising the representation level across the numbered series and fold in a few spin-offs, there is ample scope for a second FF expansion
The buff Don Andres gives to stolen creatures as well as the Treasure tokens he generates when you cast noncreature spells that don't belong to you are nice, but they're far from enough to make stealing cards worthwhile (especially because the treasures enter tapped)
Either your opponents get dead quicker, or youre going to be targeted out