Does Immortal Phoenix get its +2 assault bonus when moving to an empty battlefield if an opponent plays Void Seeker during the showdown?

Ruling: No, Immortal Phoenix does not get the +2 assault bonus. Even if there's a showdown on an empty battlefield, if you're alone there, there's no combat, so there are no attacking/defending units.

Nuances:

• The assault bonus only applies when there is actual combat with attacking/defending units
• A showdown can occur on an empty battlefield, but this doesn't create combat by itself