Can a Defender play Defy on Ride the Wind after drawing it from a Stupefy that resolved during the showdown chain?

Ruling: No, you cannot Defy Ride the Wind after the showdown has begun because Ride the Wind has already resolved. You cannot start a showdown while a chain is present (in a closed state).

Sequence:

• Ride the Wind resolves first, moving and readying the unit
• Showdown begins after Ride the Wind fully resolves
• Any Stupefies played during the showdown are on a new chain
• Cards drawn from those Stupefies cannot target the already-resolved Ride the Wind

Nuances:

• You CAN Stupefy in reaction to Ride the Wind being played (before showdown begins), then if you draw Defy from that Stupefy, you can play Defy targeting Ride the Wind on the same chain
• Players pass priority between each card resolving on a chain, allowing responses at any point