If a unit in a Combat Showdown moves to a different battlefield, is it still in the showdown, will it take damage, and does it keep damage from other sources through cleanup?

Ruling: Units must be at the contested battlefield to deal or take combat damage from a Combat Showdown. If a unit moves to a different battlefield, it will not take damage from the showdown. All units everywhere heal during cleanup, so any damage from other sources (like Void Seeker) is removed.

Sequence:

• Combat Showdown is started with units at a battlefield
• If a unit moves to a different battlefield, it no longer deals or takes combat damage from the showdown
• During cleanup, all units everywhere heal, removing any damage marks