If I move a battlefield open and my opponent activates Ride the Wind and move a unit, what unit is attacker and defender?

When you move a unit to an open battlefield and your opponent uses Ride the Wind to move a unit there during the resulting showdown, the attacker and defender designations are determined as follows:

• Attacker: You (the player who first moved to the battlefield and applied the Contested status).
• Defender: Your opponent (the player who moved their unit to the battlefield using Ride the Wind).

Sequence of Events

According to RiftJudge FAQ #7283 and Rule 442.1.a:

1. Initial Move: You move a unit to an open battlefield. The battlefield becomes Contested, and a showdown begins. You are the player who applied the Contested status.
2. Opponent's Response: During the showdown, your opponent plays Ride the Wind to move their unit to that same battlefield.
3. Showdown Completion: The initial showdown concludes.
4. Combat Begins: Because units from both players are present, a combat showdown begins.
5. Designations:
   • You are designated as the Attacker because you were the first to apply the Contested status to the battlefield (Rule 442.1.a.1).
   • Your opponent is designated as the Defender (Rule 442.1.a.2).

Nuances

• "Surprise Defense": This interaction is colloquially known as a "surprise defense" or "active defense."
• Triggers: "When I defend" abilities on your opponent's units will activate when the combat begins, as they are the defender. Conversely, "When I attack" abilities on your units will activate as the attacker.
• Conquering: If your opponent (the defender) wins the combat, they can conquer the battlefield and score a point, provided they have not already scored that battlefield during the current turn.

This ruling is based on the established mechanics for Contested status and combat designations as documented in the Riftbound rules and FAQs.