When do runes get recycled for playing cards?

Runes are recycled to pay for a card's Power cost during the "Pay the card's costs" step of playing a card.

According to Rule 354.1, when playing a card, you must pay the combined Energy cost and Power cost. During this specific step, you may use activated abilities with the [Reaction] tag—such as the "Recycle this" ability found on all Basic Runes—to add resources to your Rune Pool to cover those costs.

The Sequence of Paying Costs:

1. Determine Total Cost: You first calculate the base cost of the card and apply any modifiers (increases, decreases, or discounts).
2. Pay Costs: This is the step where you actually provide the resources.
   • If you need Power of a specific Domain, you can use the [Reaction] ability on a rune (either ready or already exhausted) to recycle it.
   • Recycling the rune adds the corresponding Power to your Rune Pool, which is then immediately spent to satisfy the card's Power cost.
   • As noted in Rule 403.3, the action of recycling must be able to be completed for the cost to be paid.

Key Nuances:

• State of the Rune: You can recycle runes in either state (ready or exhausted). If you have an exhausted rune, you can recycle it to pay for a Power cost (RiftJudge FAQ #4296, #4065).
• Timing: Recycling is a reaction ability. You perform this action while you are in the process of paying the costs for the card you are playing.
• Rune Deck: When a rune is recycled, it is returned to the bottom of your Rune Deck, not the Main Deck (Rule 403.1.b).