Andeonium Hive is roughly circular, with large habunits and mining facilities on the lower floors. The main Chaos force attacked from the South, with contingents of Alpha Legion and World Eaters circled round and advanced from the East and West. PDF troops held the city, but were harassed by Daemon and guerrilla forces. The Aeldari arrived from the Northwest at the same time as the loyalist Space Marines arrived from the East.
From an unknown source, a formidable force of Tyranids appeared in the western part of the research facilities on the upper levels, as well as some Drukhari raiders.