When Leona Legend's ability triggers during a showdown after a chain resolves, does it create a new chain, is it still a showdown, and can players respond with action cards or only reactions?

Ruling: Leona Legend's triggered ability creates a new chain that can be responded to with reactions. Showdowns do not end when a chain resolves - both players must pass focus in sequence before a showdown ends.

Sequence:

• Rune Prison resolves on the initial showdown chain, stunning the attacker
• The chain ends
• Leona Legend triggers and creates a new chain
• Players can respond to this new chain with reactions
• Both players must pass focus in sequence for the showdown to end

Nuances:

• Players are limited to reactions when responding to the new chain during the showdown, not action cards like Hextech Ray