Though the game has already been unveiled, PlanetSide Goes Underground This October With PlanetSide Core Combat, Its First Expansion is the press release officially announcing the add-on for SOE's MMOFPS (thanks Frans). Here's the product in a nutshell: "PlanetSide: Core Combat adds a new style of gameplay to PlanetSide with head-to-head urban warfare, testing players' skills as they react quickly to enemy troops in high-adrenaline fire-fights in subterranean alien complexes. With six new underground war zones, additional weapons, vehicles, and enhanced empire bonuses, Core Combat creates a new dimension for players to master in PlanetSide's all-hours-of-the-day online conflict."