If a spell's target is removed before the spell resolves (e.g., via Retreat), does the spell fizzle or must it retarget to another valid target?

Ruling: Spells do not fizzle in Riftbound. Targets are chosen when an effect is finalized on the chain and cannot be changed. When the spell resolves, if the target is no longer legal, that part of the spell does nothing (do as much as you can), but the spell still resolves and any other effects still happen.

Sequence:

• Targets are declared when an effect is finalized on the chain
• If a target becomes illegal before resolution, that part does nothing
• The spell still resolves and performs any other effects that don't require the illegal target
• The spell cannot retarget to a different unit

Nuances:

• Cards with reflexive triggers (like Falling Star) are more complex - targets for the reflexive triggers are chosen when the triggers are added to the chain, not when the original spell is played
• If you respond to Falling Star before it resolves (before triggers go on chain), the triggers must still choose valid targets when added, which could include your own units
• If you respond after the triggers are on the chain with targets already chosen, those targets cannot change