Can Lux - Crownguard be used to pay the cost of Hard Bargain?

Ruling: No, Lux - Crownguard cannot be used to pay for Hard Bargain's effect cost because Lux can only be used to play spells, not to pay for effect costs like "counter a spell unless its controller pays 2."

Nuances:

• Deflect is different because it changes the cost of the spell when you play it (an additional cost)
• Hard Bargain's cost is not linked to the playing of the spell itself; it makes you pay an additional cost or something bad happens to your spell after it's played