PM-1203 was a large asteroid that supported a thin atmosphere. It was one of the numerous asteroids that composed the shattered remains of the planet Anaxes.
During the Clone Wars, the Galactic Republic established Fort Anaxes, a military base which served as the Republic's command center during the Battle for Anaxes. Following a cataclysmic disaster that destroyed the planet but miraculously spared the base, Fort Anaxes was abandoned and eventually inhabited by a colony of Fyrnocks.
Unaware of this, the Rebellion chose the base as a drop point for supplies for the crew of the Ghost, which led to a battle between them and the Fyrnocks. Later, the Ghost crew lured The Grand Inquisitor and a force of Stormtroopers here so that the Fyrnocks could ambush them, leading to a battle between the two forces that ended with the rebels' escape.