Can you float runes during a showdown?

Yes, you can float energy and power from runes during a showdown.

According to RiftJudge FAQ #2353, you can exhaust runes to add energy (or power) at Reaction speed during an opponent's turn, including during a showdown. This energy will then float in your rune pool until the end of the turn.

Key Rules and Nuances:

• Reaction Speed: Because floating energy is an activated ability of your runes, it can be performed any time you have priority or when you are paying costs for a card or effect.
• Timing: You can float resources before or during the resolution of a chain, provided you have priority.
• Persistence: Once added to your rune pool, energy and power remain available until the end of your draw phase or the end of your turn (Rule 166).
• Strategic Use: As noted in the FAQs, this is a common strategy to prepare for playing cards later in the turn or to pay for costs that arise mid-resolution (such as when a card asks for costs to be paid after it finalizes).

Important Note: If you are in a showdown and both players pass priority without anyone playing a card or floating resources, the opportunity to act on that specific chain passes. Always ensure you float your resources before passing priority if you intend to use them for a subsequent action.