The Phall System consisted of two habitable agri worlds, Phall I and II. Both were recorded as peaceful, loyal to the Imperium, and lightly populated. The System became infamous during the Horus Heresy for being the site of a major battle between the Imperial Fists and Iron Warriors.
Due to the special significance the Phall System held for the Imperial Fists, after their division into Chapters as per the Codex Astartes, the system was the focal point of the secret "Last Wall Protocol". If Terra itself was under dire threat, all of the Imperial Fists successors would meet at Phall to discuss reunifying once more into a Legion with or without the approval of the Senatorum Imperialis. The protocol was enacted during the War of the Beast.
- 1: The Horus Heresy Book Three - Extermination, Chapter "The Battle of the Phall"
- 2: The Emperor Expects (Novel) Chapter 14