Can Kaisa's 'Daughter of the Void' ability be used to pay the power cost to hide a hidden spell?

Ruling: No, Kaisa's ability cannot be used to pay the power cost to hide a spell. The ability can only be used to play spells, and hiding is not the same as playing.

Nuances:

• Hiding can consist of units or gears as well as spells, so it would be impossible for an opponent to know if you truly hid a spell without revealing what you're hiding first