What costs do you pay when hiding a card facedown, and do you pay anything when revealing/playing it from hidden?

Ruling: When you hide a card, you pay 1 Power of any domain (not the card's energy cost). When you play the card from hidden later, you pay no additional costs.

Sequence:

• To hide a card: Pay 1 Power (by recycling a rune or using other power-generating abilities)
• To play from hidden: Pay nothing (the card is played for free)

Nuances:

• Power costs are paid by recycling runes (not just tapping them), or through other abilities that generate power (like Kai'Sa legend, Malzahar, or seals)
• The 1 Power to hide can be paid with any domain/seal
• The rune recycled for power can be one that is already tapped
• If playing the card directly from hand (not from hidden), you would pay its normal energy cost in the upper left