Tartarus

Tartarus was an Imperium Civilized World that was laid seige to early in the game Dawn of War. It would appear in one campaign, as later expansions would take place on other world and systems.

In Dawn of War
The game begins on Tartarus, a world besieged by Ork attacks. The local Imperial Guard, lead by Colonel Brom, struggled to contain an Orkish attack force until the Blood Ravens 3rd Company arrived. The Blood Ravens, lead by Captain Angelos and Librarian Isador Akios, start a campaign to eliminate the massive Waaagh! that has come of Tartarus. Captain Angelos leads the Blood Ravens, aided by the Imperial Guard, to several victories against the Orks, but later they are met by Inquisitor Mordecai Toth who encourages them to leave the world. Toth tells them that a Warp storm was en route and would arrive in a few days. The storm would strand them all, even the Orks and civilians, on the surface of the planet.

As the evacuation of the civilian population of Tatarus began, the Blood Ravens continue the fight against the Orks. It is later discovered that the Ork invasion is a ploy by Chaos forces. The Alpha Legion, lead by the Sorceror Sindri and the Chaos Lord Bale, rallied the Orks against the Imperium world as major distraction, while the Chaos forces hunted an artifact of unknown potential. It is found out that the Eldar forces under Farseer Macha have also arrived on Tartarus as well to combat the Chaos forces.

Later, more information comes to light about the Chaos artifact. It was a stone called the "Maledictum," and it contained a daemon of Khorne of great power. As the Blood Ravens marched, Chaos forces almost succeeded in releasing the daemon in the Maledictum. At the end of the last battle in the campaign, Chaos forces had been destroyed by the Blood Ravens, though the daemon Maledictum had been freed, and the Eldar forces present were severely crippled. The civilian population of Tartarus had evaporated as most were killed by the Orks, and the rest had already fled; the cities on Tartarus had been destroyed, the greatest concentration of Chaos on the surface had greatly changed the landscape around them, and finally Tartarus had been consumed by the Warp storm after the end of the campaign. It is revealed to Captain Angelos in the end that the entire world of Tartarus was essentially a sacrificial altar, and every death had contributed to empowering the daemon in the Maledictum.