Fast effects, priority and the Cascade

Fast effects (every Ambush and every effect marked Fast) may be used by the turn player in their own Preparation Phase and Combat Phase, outside a battle.

They may also be used by either player in a response window while that player holds priority: in the opponent's turn, this is the only way.

No Fast effects can be used in the Emplacement Phase (7.4.2).

A response window opens when an attack is declared (9.5.2), when an effect is put on the Cascade outside a window (an activated effect, a cast Event, a sprung Ambush) and when triggered Timing Effects are placed (12.5). An effect used in answer joins the open window; it doesn't open a new one.

A window also opens when optional Timing Effects have been triggered, so their controllers can use them.

In a window, the turn player holds priority first. A player with priority either responds (uses a Fast effect or an offered Timing Effect) or passes; then priority goes to the other player.

While nobody has responded yet, the window closes only when both players have passed one after the other.

Once someone has responded, a single pass closes the window, and the Cascade resolves.

ExampleYour opponent casts an Event, you spring an Ambush in answer, and your opponent passes. The window closes: your Ambush resolves, then their Event.

The game passes for a player automatically when they have no response anyone could see: no face-down Ambush under one of their Souls in the Front Line, no offered Timing Effect and no Fast effect on a face-up card. So an automatic pass reveals nothing that was hidden.

The Cascade is a stack of effects waiting to resolve. A new effect goes on top; the effect on top resolves first.

When the window closes, the Cascade resolves from top to bottom, one effect after another, without interruption. No one can add to it while it resolves.

Timing Effects triggered while the Cascade resolves wait until it has finished. Then they go on a new Cascade, with a new window (12.5.2).

An effect that resolves in parts ("… then …") resolves one part at a time; Instant Effects triggered by a part resolve before the next part begins.

Instant Effects resolve at once, before anything else continues: first the turn player's, then the opponent's. Each player puts their own in the order they like. Before they resolve, the game captures every Soul at 0 HP (14.4.2), except in the fight step of a battle (9.5.6); an Instant Effect whose card is no longer active by then does nothing.

Then mandatory Timing Effects go on the Cascade: first the turn player's, then the opponent's, each in the order their controller likes. So the opponent's resolve first.

Then a window opens in which both players may add optional Timing Effects and Fast effects, starting with the turn player.

When two identical effects of the same card trigger together, the game orders them for you; the order makes no difference.

An effect that answers being targeted ("The Ambusher is targeted by an Effect") can be used only in the window in which the targeting effect went on the Cascade, while that effect is still on top.

Being targeted includes having one's Soul Spot targeted, with or without a condition on the Soul (11.4.4).

Instant Effects never go on the Cascade, so they can't be answered this way. Effects that hit "the attacker" or "the attacked Soul" (like Defiance) do not target at all.