Can you exhaust runes at the end of your opponent's turn to float energy into your draw step, and if so, can you use that energy to play action speed cards before your draw step ends?

Question

Accepted Answer

No. You cannot exhaust runes at the end of your opponent's turn to “float” Energy into your upcoming draw step. Rune Pools empty at the end of each player's turn, so any Energy you add during your opponent's end-of-turn will be lost at that end step and will not be available during your draw step. Even if Energy is added and retained, you may only spend Energy after it has been added to your Rune Pool and in timings where the game allows you to play cards; Add abilities finalize immediately when they Add Energy [429.2] and Add Reactions can be used while paying costs [429.3] and to pay for plays [357.1.a], but they cannot circumvent the emptying at end of turn [166].

You cannot float Energy across the end-of-turn boundary. Any Energy added at the end of your opponent's turn will be lost at that end of turn per the Rune Pool emptying rule [166], so it will not be available during your draw step. Playing action-speed cards before your draw step ends would also require that the Energy be in your Rune Pool at the appropriate timing and that the game permits playing those cards at that point; the relevant resource rules do not allow the Energy to persist across the end of your opponent's turn [166], and Add abilities finalize immediately when they add resources [429.2].

At your opponent's end of turn, triggered and activated abilities can be placed on and resolve on the chain; if you have an ability that Adds Energy and you activate it there, the Add finalizes and puts that Energy into your Rune Pool immediately [429.2]. However, rule [166] says every player's Rune Pool empties at the end of each player's turn. That means any unspent Energy in your Rune Pool will be lost at that end-of-turn moment [166] and will not persist into your draw step. Because you must have Energy in your Rune Pool in order to spend it to play cards or pay costs [165.2], and because Rune Pools are emptied at the end of the turn [166], Energy added during your opponent's end step cannot be carried forward into your draw step. If you add Energy during your own draw phase (not covered in detail here), that Energy would remain until the end of your draw phase (since Rune Pools empty at the end of the draw phase) and could be spent to pay costs; Add abilities that are Reactions can be used while paying costs [429.3] and Add finalizes immediately [429.2].

If an ability adds Energy as part of resolving during the very last part of your opponent's turn, the emptying effect in [166] still applies at 'the end of each player's turn.' The provided rules text does not give a separate ordering that would allow Energy added after the emptying to persist, so the safest reading is that Energy added during that end-of-turn window is still subject to the end-of-turn emptying. Some cards have templated text that limits when added Energy can be spent (for example, Diana - Scorn of the Moon says 'Spend this Energy only during showdowns'). Even if you could retain Energy, domain- or card-specific restrictions may prevent its use except at certain timings. Add abilities that are Reactions can be used during the Pay Costs step to help pay for plays initiated at that moment [357.1.a] [429.3]. This means you can use Reactions that Add to pay costs for a play that is being made right then, but you cannot use Energy added earlier at your opponent's end-of-turn (because of [166]). If a play is initiated on your turn and you attempt to use an Add Reaction while paying its costs, that Add Reaction must be legal to activate at that timing; Add abilities themselves cannot be reacted to if the card text forbids reacting to Add abilities (see card-specific notes such as on Diana - Scorn of the Moon).

The core reason you cannot "float" Energy across your opponent's turn is the Rune Pool emptying rule. Rule [166] explicitly states that every player's Rune Pool empties at the end of each player's turn and at the end of each player's draw phase, and that any unspent Energy or Power are lost. That timing point sits at the end of the turn, so Energy you add during your opponent's end-of-turn window will be subject to that emptying and be lost. Adding Energy itself is immediate when an Add ability resolves: spells, triggered abilities, and activated abilities that Add resources finalize immediately [429.2]. Activated Add abilities that have the Reaction tag can be used while paying costs when playing spells or abilities (see [357.1.a] and [429.3]), so they are useful for paying costs being initiated on that same player’s turn. But those rules do not override the Rune Pool-emptying timing. Put simply: you can use Add Reactions to help pay costs while you are playing something (including during the Pay Costs step) [357.1.a] [429.3], and when an Add resolves the Energy enters your Rune Pool immediately [429.2], but because Rune Pools are explicitly emptied at the end of each turn [166], you cannot add Energy at the end of your opponent's turn and keep it into your draw step. Also note that some cards place additional restrictions on when the Energy they add may be spent (for example, Diana - Scorn of the Moon’s Energy can only be spent during showdowns), so even Energy that survives timing rules might still be unusable for certain plays. Given the rules text provided, the most defensible ruling is that you cannot float Energy across an opponent's turn into your draw step, and therefore you cannot use that floated Energy to play action-speed cards before your draw step ends.