Does a spell fizzle if all its targets become illegal before it resolves?

When a spell or ability tries to resolve, the game first checks whether its targets are still legal (still in the correct zone, still a valid type, still not protected, etc.). This check is governed by CR 608.2b: if all targets are illegal at that moment, the spell or ability is countered by the rules — it simply ceases to exist without resolving, and its effects never happen.

This is informally called "fizzling." It is distinct from a spell being countered by another spell like Counterspell; the result is the same (the spell goes to the graveyard and does nothing), but the mechanism is a rules-based counter, not a spell or ability counter.

If a spell has multiple targets and only some become illegal, the spell does not fizzle. Instead, it resolves and simply ignores the illegal targets, affecting only the remaining legal ones (CR 608.2c). Fizzling only occurs when every single target is illegal.

Concrete example: You cast Lightning Bolt targeting your opponent's Grizzly Bears. In response, your opponent casts Giant Growth on the Bears — that doesn't help. But if instead they cast Blink of an Eye to bounce the Bears back to their hand, the Bears are no longer on the battlefield and are no longer a legal target. When Lightning Bolt tries to resolve, it has no legal targets and is countered by the rules; it goes to your graveyard and deals no damage.

The key rules references are CR 608.2b (all targets illegal → countered by rules) and CR 608.2c (some targets illegal → resolve affecting only legal targets).