Spellskite

If a spell or ability has a variable number of targets, you can't change the number of targets.

If Spellskite leaves the battlefield before its ability resolves or otherwise becomes an illegal target for the target spell or ability before its ability resolves, no targets are changed.

You can activate Spellskite's ability even if Spellskite isn't a legal target for the target spell or ability—or even if that spell or ability has no targets. In this case, no targets are changed.