When a player moves to an unoccupied battlefield starting a showdown, can the defending player use an action like 'Ride The Wind' to move a minion to the battlefield and become a defender?

Ruling: Yes, the defending player can use actions to move minions to the battlefield. The player who first moved to the unoccupied battlefield is the attacker, and the other player is the defender.

Sequence:

• Player A moves to an unoccupied battlefield (becomes the attacker)
• Player B is the defender
• Chains work basically the same as occupied showdowns
• The defender can respond with actions like Ride The Wind to move minions to the battlefield

Nuances:

• The main difference from occupied showdowns is there are no "when I attack/defend" triggers in unoccupied showdowns
• A minion moved in this way by the defender counts as a defender (referred to by one user as a "hidden defender" since they moved when the player is attacking)