During a showdown, who has priority to play the first action, and how does priority work after an action resolves?

Ruling: During a showdown when the initial chain is resolving and the chain is empty, the attacker gets focus and priority. After an action resolves, priority goes to the owner of the next effect on the chain if the chain is not empty; if the chain is empty during a non-initial chain, the next player (not the owner of the most recent effect) gets focus and priority.

Sequence:

• During showdown, initial chain resolving, chain empty: attacker gets focus and priority
• During showdown, initial chain resolving, chain not empty: owner of next effect on chain gets priority
• During showdown, not initial chain, chain empty: next player (after owner of most recent effect) gets focus and priority
• During showdown, not initial chain, chain not empty: owner of next effect on chain gets priority
• Outside showdown, chain empty: current turn player gets priority
• Outside showdown, chain not empty: owner of next effect on chain gets priority

Nuances:

• Action speed cards can only be played on your turn when the chain is empty OR by either player during a showdown when they have focus and the chain is empty
• If you have two Last Breath cards and priority with an empty chain during showdown, you can play one, but after it resolves the other player gets priority (assuming it's not the initial chain)