Does moving a unit to an empty battlefield count as an attack for triggering effects like Mask's +1 buff?

Ruling: Moving to an unoccupied battlefield is not attacking and does not trigger attack-related effects. However, if an opponent later moves a unit to that battlefield during the Showdown (such as with a spell), you will be designated the attacker since you were the first player to make that battlefield contested.

Nuances:

• If you already have a unit at a battlefield and then Charm an opponent's unit to that battlefield, you will be defending and will get the Mask buff as a defender.