The Order Civil War, also referred to as the War for Armageddon was a period of political and military instability which led to the fall of the Order. The Civil War led to the deaths of hundreds of millions and the rise of the Apocalyptar as a dominant armed force.
Beginning in the late Order Era, Panthea's discovery of the Rubicon of Night led to the creation of a rogue militant faction loyal to Polaris. As the anti-Order forces led by Orcus rampaged through the Seven Galaxies, murdering millions in the process, the Order splintered as a faction of Secessionists rose up to seek independence. The War came to its climax at the Great Battle of the Elysian Fields, which led to the destruction of the Order of the Occult Rangers and formally ended the Order.
The Order Civil War is the most deadliest conflict to have ever occured within the Seven Galaxies, with the second most deadliest conflict having only a third of the war's overall casulties.