Phalanx

Phalanx is the massive starship that serves as the mobile fortress-monastery of the Imperial Fists Space Marine Chapter and was constructed many millennia ago by unknown hands during the Dark Age of Technology long before the Age of the Imperium. Phalanx itself is gigantic, the largest starship known to have been constructed by Human hands, and something of its magnitude has not been seen since the Age of Technology. The size of a small moon or large asteroid, its foredeck can dock a dozen Imperial Navy cruisers around its circumference. The vessel is essentially a hive city in space, with its great spires reaching towards the stars, giving it the appearance of a giant mace-head. In many ways, Phalanx is the only vessel ever built by Mankind that comes close in size and complexity to that of the Aeldari’s craftworlds.