For Rek'Sai's legend ability (reveal top 2 cards after conquering and play 1): If you find a seal and have no tapped runes, can you tap a rune for floating mana and then recycle it to pay the seal's power cost?

Ruling: Yes, you can tap a rune for floating energy and then recycle it to pay the seal's power cost when playing the card from Rek'Sai's ability.

Sequence:

• Rek'Sai's ability puts the card on the chain pending when you choose to play it
• After the ability resolves, the card is finalized during the following cleanup
• During step 4 of the finalization process, you pay costs
• When paying costs, you can activate rune add abilities (tap a rune for energy, then recycle it for power)
• This works even though you don't normally have priority during combat resolution, because you are paying costs at this timing

Nuances:

• You can only activate rune abilities when you have priority OR when an effect asks you to pay costs
• You cannot activate rune abilities during spell/ability resolution unless the effect specifically instructs you to pay costs during resolution
• The card is played directly from your main deck to the chain (not from banish)