If I use Accelerate to play a unit during my opponents turn, can they respond with a Reaction spell before my unit resolves?

Question

Accepted Answer

Yes — if you legally play a unit with Accelerate during your opponent's turn (for example because that unit has Reaction or another effect that permits playing it then), that play goes on the chain like any other play and your opponent can respond with a Reaction spell before the unit resolves. Accelerate is an additional cost paid while playing the unit and does not prevent responses.

If the unit is legally being played during your opponent's turn (e.g., it had permission via Reaction), paying Accelerate is part of the play [805.2] and the play goes on the chain so the opponent may add a Reaction spell in response if they have one playable at that timing [813.1.b] [813.1.c.1]. Accelerate does not stop responses and only affects the entering state of the unit (it enters ready if Accelerate was paid) [805.6] [FAQ:unleashed#24]. If the unit could not legally be played during the opponent's turn (it lacks Reaction or another permission), you cannot play it in that timing to begin with [813.3.a].

You begin playing the unit and, as part of playing it, choose to pay the Accelerate additional cost [805.2]. That play is a play action and is put on the chain, just like any other card play (players receive opportunities to respond while the item is on the chain) [813.1.b] [813.1.c.1]. Before the play resolves, the opponent may add a Reaction spell to the chain if that Reaction is legal to play at that timing (Reaction permits play during Closed States and grants Action permissions) [813.1.c.1]. Players resolve the chain in reverse order; if the opponent's Reaction removes, counters, or otherwise affects the pending play, that will affect whether the unit ever resolves and enters the board. If the unit's play resolves and Accelerate was paid, the unit will enter ready rather than entering exhausted then becoming ready [805.6] (see also example in [FAQ:unleashed#24]).

If the unit does not have Reaction and no effect grants permission to play it on the opponent's turn, you cannot play it during your opponent's turn at all — there is nothing for the opponent to respond to in that timing because the play was illegal [813.1.c.1] [813.3.a]. If the opponent's Reaction moves the unit to a non-board zone while it's on the chain, targeting/relationships between that play and the unit may be severed per the targeting/resolution rules and related FAQs [359.3.e.12] [FAQ:unleashed#22]. If the opponent's Reaction successfully counters or otherwise prevents the play, the unit will not resolve and will not enter the board; Accelerate only affects how the unit enters if the play actually resolves [805.2] [805.6]. Even if the unit kills something as part of its additional cost or play, Accelerate’s delayed replacement effect still causes it to enter ready if Accelerate was paid (see [FAQ:unleashed#24]).

Playing a unit and paying Accelerate. Accelerate is an optional additional cost you pay as you play the unit, and must be paid during the steps of playing that card — it is not something you can pay while the unit is already on the board [805.2]. If you are playing the unit during your opponent’s turn, that must be legal (for example the unit or another effect granted the permission to be played then, such as the unit having Reaction) because normal plays are restricted to certain timings [813.1.c.1] [813.3.a].

Putting the play on the chain and responses. A play is put on the chain like other plays, and Reaction grants the card the permissions of Action so it may be played during Closed States on any player's turn and otherwise functions as allowed by Action’s permissions [813.1.b] [813.1.c.1]. Because the play goes on the chain, the opponent gets the normal opportunity to respond by adding their own Chain items — including Reaction spells that are legal to play at that timing — before the unit play resolves.

What Accelerate does to resolution. Paying Accelerate only changes how the unit will enter the board (it will enter ready) and does not prevent opponents from responding to the play while it is on the chain [805.6]. See the official clarification example where Atakhan still enters ready if Accelerate was paid even though interactions happened during its play ([FAQ:unleashed#24]).

Therefore: if you legally play a unit during your opponent’s turn (e.g., it has Reaction), the opponent can indeed respond with a Reaction spell before the unit resolves. If the play is illegal (the unit has no permission to be played then), you cannot play it in that timing to begin with.