Intervene
Urza's Legacy — common
Instant
Intervene rulings:
2004-10-04: If a spell is modal, use the target(s) of the current mode only for this check. Targets for the other modes are never selected.
2004-10-04: Intervene can only target a spell that is currently targeting a creature.
2004-10-04: It means “targeting at least one creature” not “exactly one creature”.
2004-10-04: If the spell’s target leaves the battlefield before this spell resolves, Intervene won’t resolve since it no longer targets a spell that targets a creature.