What happens when one of the world's best tower defense games meets one of gaming's most beloved power-mad robotic villains? Fans line up to pay $4.99 or 400 Microsoft points for the Defense Grid: You Monster expansion, that's what.

Coming December 7 to Xbox Live Arcade and Steam, Defense Grid: You Monster is the first full story expansion for the award winning futuristic tower defense game, featuring eight new maps, 35 challenge missions, and one hell of a crazy cameo.

Warping her way over from Valve's Portal franchise, GLaDOS is extremely curious about what the player and his more civilized artificially intelligent computer are doing with all of these towers, and when the all-powerful machine scientist gets curious, it's time for some tests. Players will be responsible for managing their defenses across a series of Portal-themed levels. That, and dying. Lots of dying. Don't worry; it's all for science.

On December 7th Portal's GLaDOS comes to Defense Grid [Hidden Path Entertainment]