When an opponent plays Hidden Blade targeting a unit with Deflect, and you want to Defy the Hidden Blade, does the opponent still have to pay the Deflect cost?

Ruling: Yes, the opponent must pay the Deflect cost even if you Defy the Hidden Blade. Deflect costs are paid during finalization, which happens before the opponent passes priority and before you can respond with Defy.

Sequence:

• The spell is cast and goes onto the chain as pending
• The spell finalizes (targets are chosen and Deflect costs are paid during this step)
• The caster passes priority
• The opponent can now respond with cards like Defy

Nuances:

• Defy only looks at the printed base cost of a card, not additional costs like Deflect
• A card like Sky Splitter cannot be Defied even if played for reduced energy cost, because Defy checks the base printed cost
• Multi-target reflexive spells like Icatian Rain work differently: the spell itself finalizes with no targets, then when it resolves it creates reflexive triggers that each finalize separately with their own targets and Deflect costs