Utterlost

Utterlost was the site of one of the Thousand-Year Battles of the War in Heaven.

The most re-fought temporal conflict occurred there, to the point that no one knew whose colony it was originally. Unapproachable by normal means, attempts were made to expand the battle using zero time without success. Kaiwar and Mohandassa were considered possible side-effects of the fighting on Utterlost. (PROSE: The Book of the War)

The Utterlost Accords were a series of negotiations between the Great Houses and the enemy. (PROSE: Pre-narrative Briefing B)