If a unit moves to a battlefield during an ongoing showdown at a different battlefield, does the new showdown interrupt the current one, or does the current showdown finish first?

Ruling: The ongoing showdown must always finish completely before a new showdown can begin at a different battlefield.

Sequence:

• Player A moves Kaisa Survivor to a battlefield, triggering a showdown
• Player B plays Ride the Wind during this showdown to move a unit to the opposite battlefield
• The original showdown with Kaisa finishes completely (including drawing the card from conquering)
• Only after the first showdown is fully resolved can the new showdown at the opposite battlefield begin

Nuances:

• A new showdown can only start in a neutral open state: no chain (all triggers resolved) and no showdown already in progress