Does Sudden Storm deal 4 damage when a unit attacks an open battlefield?

Ruling: No, Sudden Storm does not deal 4 damage when moving to an open battlefield because moving to an open battlefield does not result in combat or attacking—it only starts contesting that battlefield. The 4 damage effect only applies if there is either a unit already there or a unit moved in during the showdown, making the first unit designated as an attacker.

Sequence: (when a unit moves in during showdown)

• A unit moves to contest a battlefield
• If another unit moves in during the showdown, both players must pass with focus in succession
• The showdown closes and combat opens
• Unit designations (attacker/defender) are applied
• Sudden Storm's 4 damage effect can trigger

Nuances:

• Simply moving to an open battlefield does not create an attacker designation
• If a unit moves in during the showdown, you must wait until combat opens before designations are applied