If Fiora is targeted by Void Seeker and buffed in response, does the opponent have to play Deflect?

Ruling: No, the opponent does not have to play Deflect. Deflect costs are paid at the time targets are chosen, not when the spell resolves.

Nuances:

• Buffing Fiora after she's been targeted doesn't change whether Deflect needs to be paid
• The timing of when Deflect costs are determined is at target selection, not resolution