If my opponent starts a showdown and I use Zenith Blade while defending to move my unit to the same battlefield where the showdown is taking place, am I still the defender or the attacker?

Ruling: You remain the defender. Attacker and defender roles are determined when combat starts and do not change during the combat.

Sequence:

• Opponent initiates showdown on a battlefield you control
• You are designated as the defender at this point
• You use Zenith Blade to move your unit to that battlefield
• Your role as defender does not change

Nuances:

• The defender/attacker roles are determined by who controlled the unit that applied the contested status (initiated the showdown)
• If you controlled the battlefield when the showdown started, you are the defender
• Roles do not change once combat has started, regardless of unit movement