A universe... at war. In videogames, it almost goes without saying. A universe in blissful unity isn't exactly a well-explored fictional backdrop. This is a science-fiction wargame. The universe is going to be at war.
The problem facing Gas Powered Games is that it needs to feel like that. Supreme Commander had the sort of mechanized destruction that made other RTS games look like a slap-fight. To make the add-on pack mean anything, they need to raise the stakes. How do you raise the stakes when you already have a trio of huge, genocidal factions?
By introducing something even bigger. Big enough to make the Cybran, UEF and Aeon Illuminate combine against the new threat. Enter the Seraphim, the antagonists in Alliance's main campaign and a fully playable faction in multiplayer. Veterans of Supreme Commader will remember the Aeon gained their technology from an alien race who were wiped out. These are the Seraphim, except what was wiped out was actually a tiny colony, not the entire race. They're back, looking for revenge, and not the pacifists the Aeon were inspired by, but warrior-monks dedicated to victory or death. And they've got the sort of technology that makes your average UEF tank look like a pop-up toaster.
"They use powerful units that are slightly similar to the Aeon," says Producer Jeremy Ables, "but the Seraphim units are less specialized, which lets them handle a variety of combat situations with a single unit."