608.2b If the spell or ability specifies targets, it checks whether the targets are still legal. A target that's no longer in the zone it was in when it was targeted is illegal. Other changes to the game state may cause a target to no longer be legal; for example, its characteristics may have changed or an effect may have changed the text of the spell. If the source of an ability has left the zone it was in, its last known information is used during this process.
The spell or ability is countered if all its targets, for every instance of the word "target," are now illegal. If the spell or ability is not countered, it will resolve normally. However, if any of its targets are illegal, the part of the spell or ability's effect for which it is an illegal target can't perform any actions on that target or make that target perform any actions. The effect may still determine information about illegal targets, though, and other parts of the effect for which those targets are not illegal may still affect them.
Example: Sorin's Thirst is a black instant that reads, "
Sorin's Thirst deals 2 damage to target creature and you gain 2 life." If the creature isn't a legal target during the resolution of
Sorin's Thirst (say, if the creature has gained protection from black or left the battlefield), then
Sorin's Thirst is countered. Its controller doesn't gain any life.
Example: Plague Spores reads, "Destroy target nonblack creature and target land. They can't be regenerated." Suppose the same animated land is chosen both as the nonblack creature and as the land, and the color of the creature land is changed to black before
Plague Spores resolves. Plagues Spores isn't countered because the black creature land is still a legal target for the "target land" part of the spell. The "destroy target nonblack creature" part of the spell won't affect that permanent, but the "destroy target land" part of the spell will still destroy it. It can't be regenerated.
RULINGSMomentary Blink9/25/2006 When
Momentary Blink resolves, the creature is exiled, then immediately returned to the battlefield.
The game sees the returning card as a different permanent from the one that left the battlefield. Any counters, Auras, and so on are removed.
Any spells or abilities targeting the creature no longer target it.Beacon of Destruction7/15/2007 If a Beacon is countered, it’s put into its owner’s graveyard, not shuffled into the library.