One of the two moons of Mars, Phobos is an ancient Martian construct designed as some kind of super weapon. While its ultimate purpose is unknown, it served as the control unit for the Disorder units and was capable of destroying Mars or at least damaging it enough so that humanity couldn't exist there. This moon, along with the Disorders Units, are the only two known examples of Martian technology.
During the Civil Commotion of Mars, Klein used Phobos in a last ditch attempt to destroy Mars. He commandeered a Martian weapon, fought against the Raven and was defeated. Phobos was disabled when its orbit control mechanism was destroyed by the Raven, ultimately causing it to self destruct and break up in Mars' atmosphere.