If an opponent uses Ride of the Wind to move their unit to another battlefield after I use a reaction to buff my defender, does their unit die from combat or successfully move away?

Ruling: The opponent's unit does not die. It successfully moves to the other battlefield and is no longer present at the original combat location.

Sequence:

• Defender uses a reaction to buff their unit during combat
• Attacker plays Ride of the Wind as an action in response, moving their unit to another battlefield
• The original combat resolves with the attacker's unit no longer present (defender holds the battlefield)
• After the first showdown fully ends, a new showdown starts at the battlefield where the unit moved
• Both players can play actions/reactions at this new showdown
• The new showdown proceeds through all normal steps, potentially resulting in conquest

Nuances:

• Actions can be played after reactions as part of the chain during combat
• The unit doesn't die because it's no longer at the battlefield where combat is happening
• You cannot have two showdowns occurring simultaneously; the second showdown waits for the first to complete
• Even if the destination battlefield was empty, a new open showdown starts there after the first combat ends