Invasion overlays a Team Conflict and a scene framing structure on top of normal play, forming a superstructure that can fairly adjudicate the high-level outcome of the invasion, while the details are worked out through play. The DM can thus focus on playing to make things real and make things interesting in the roleplay while going all-out to try win in the over-arching conflict. Here it is!
Just got one piece of art in this week: turns out Yuri got sick, too. It's going around, I guess. This is another of William's pieces.