When attacking a battlefield and starting a showdown, can the attacker use a reaction card (like Smoke Screen) when they have priority, or can showdowns only be started with actions?

Ruling: Yes, the attacker can play reaction cards when they have priority during a showdown. You can play any appropriately timed card (action or reaction) or activate any appropriately timed ability when you have priority.

Sequence:

• Attacker moves into occupied battlefield, starting a showdown
• Attacker has first priority during the showdown
• Attacker can play reaction spells (like Smoke Screen) before passing priority
• Opponent can respond before each spell resolves

Nuances:

• The attacker can play as many reaction spells as they like before passing to the opponent
• The opponent can respond before each spell resolves