When one player moves a unit to an empty battlefield, then the opponent uses a spell to move their unit to the same battlefield, who is the attacker and what happens with showdowns?

Ruling: The player who first caused the battlefield to be contested is the attacker, and the opponent who moved in second is the defender. Two showdowns occur in sequence.

Sequence:

• First player moves unit to empty battlefield, starting an open showdown
• Opponent plays spell to move their unit to the same battlefield, which puts another showdown on the chain
• The first open showdown must complete first, but does not result in a conquest because units of two players now exist in the battlefield
• Then immediately, a second showdown begins with the second player attacking the first player's controlled battlefield

Nuances:

• It is not possible to change the type of showdown you are in (an open showdown cannot become a contested one)
• Showdowns chain rather than transform into different types