Quake II Mission Pack: Ground Zero is the second expansion pack, released on September 11, 1998. It was developed by Rogue Entertainment. It comes with fourteen single-player levels, ten multiplayer maps, five additional music tracks, five enemies, seven power-ups, and five weapons. In the expansion's story the Gravity Well has trapped the Earth Fleet in orbit above the planet Stroggos. One of the marines who managed to land, Stepchild, must now make his way to the Gravity Well to destroy it and free the fleet above and disable the entire defenses of the planet.