Gunman Chronicles

Originally Gunman Chronicles was developed by Rewolf Software as a mod for the first-person shooter Half Life; after negotiations Sierra released it as a retail version in 2000. In Gunman Chronicles, the general of the Gunmen fell in battle against the Xenomes, a strange alien species that suddenly appeared on the planet Banzure Prime. Now a mysterious presence has tampered with the Xenome's DNA, making them bigger and stronger than ever, and the scourge is spreading once again. As Major Archer, leader of the Gunmen, the only force of order in this part of the galaxy, you must set things right - find the source of this hostile invasion and drive this alien scum from the edge of the galaxy!