Hey QM, as the Mitu War nears its conclusion, during the course of the War have we heard of or even liberated the famed Manachean Commonwealth?
Manachea iirc was the largest and most populous system of several hiveworlds under the Mitu's iron fist. It along with Port Maw (that we're probably going to build up) was Horus' primary target in the Gothic Sector during the HH. Well, that was without the Lucian Federation being a thing. It is in the least likely far bigger than Halemat.
https://warhammer40k.fandom.com/wiki/Manachean_Commonwealth>Referred to simply as Manachea by popular convention, Vysidae harbours a total population that numbers into the tens of billions. Living in one of the eleven hive-metropoli interlinked by continent-and-sea-spanning maglev transit systems, Manachea's population is highly disciplined and productive, and the world can readily rival the production capacities of more established Hive Worlds of the Segmentum Solar. It is no surprise then that Manachea Vysidae's influence not only extended to the neighbouring worlds but also into such sub-sectors as the Coronid Reach and the Cyclops Cluster. Having become the home of several Imperial administrative divisions which serve the entire region, such as the Great Tithe or the Arbites Imperialis, Manchea can easily be considered the single most important world of the entire Coronid Deeps. Manachea fields numerous regiments of highly-trained Imperial soldiers, most of them being equipped in conformity with the Solar Auxilia-template, while its industrial resource allows it to field several armoured regiments of Leman Russ Battle Tanks and even manufacture superheavy tanks in limited numbers. The seat of its Planetary Governor was the imposing Palace of Light, a fortified spire of the planetary capital, Hive Illium, where the Commonwealth's government under Pryamus Beket, Lord Protector of the Manachean Commonwealth, ruled his vast domain.I have the feeling the Manachean Commonwealth may be the Ruhr Valley to our Lucius Sector, while Lucius itself becomes Brandenberg/Berlin. Or Vice Versa, I'm not sure.