Can an attacker use an action card after the defender used an action and multiple reactions, when letting all the defender's card effects resolve? Or is there only one opportunity to play an action card at the beginning of a showdown?

Ruling: Yes, the attacker can use an action card after the defender's action and reactions resolve. Each chain resolution during a showdown passes focus to the next player, not just each individual card resolution.

Sequence:

• Defender plays action and reactions
• Chain resolves (all cards in that chain)
• Focus passes to attacker
• Attacker can now play an action card

Nuances:

• Chain resolution is different from individual chain link/item resolution
• Showdown only ends when all players pass their focus in succession without starting a new chain
• Actions can be played after chain resolution, not just after individual reaction resolutions