Phalanx

Phalanx is the massive starship that serves as the mobile fortress-monastery of the Imperial Fists Space Marine Chapter and dates back to a time before the Age of the Imperium. Officially, the homeworld of the Imperial Fists is always listed as Terra, but in reality, the Phalanx serves as the Imperial Fists' true base of operations. Originally discovered adrift in space by the Imperial Fists' Primarch Rogal Dorn, it was given as a gift to the Emperor of Mankind when Dorn was found near the Ice Hives of Inwit by his gene-father. The Emperor then returned the massive spacecraft to Dorn after he was appointed the commander of the Imperial Fists Space Marine Legion. Phalanx itself is gigantic, and something of its magnitude has not been seen since the Dark Age of Technology. The size of a small moon, its foredeck could dock a dozen Imperial Navy cruisers and its design in similar to that of a hive city in space with its great spires reaching towards the stars. In many ways, Phalanx is the only vessel ever built by humanity that comes close in size and complexity to the Eldar's Craftworlds. Phalanx is so large that it reflects light like the stars themselves, and served as a symbolic representation of the Emperor himself during the time of the Great Crusade. The vast starship is completely mobile and often follows the Chapter as it moves throughout the galaxy.