Battle of Phall
The Battle of Phall is one of the biggest space battles of the entire Horus Heresy and, given that the war took place over an entire galaxy that's saying something.
The Contenders
On team Emperor we have the Retribution fleet of the VIIth legion under command of Captain Yonnad. The Fists were known to have have the largest fleet of all the Legions.
On team Horus we have Perturabo, Primarch of the Iron Warriors and his war fleet, which consisted of some of the biggest and most well armoured starships that had ever been built.
The coming of the storm
Following the flight of the Eisenstein, Lord Rogal Dorn heard about Horus' plan to crash the Imperium with no survivors and dispatched a third of his Legion and a bigger part of his war fleet to take Horus to task. This Retribution fleet was sent ahead of the Raven Guard, Iron Hands and Salamanders who followed shortly after. Unfortunately the Retribution Fleet was marooned in the Phall system since the Chaos Gods thought that odds of 7 v 4 weren't stacked enough in their favour. Yonnad unfortunately died during the warpstorms and command was thrust on one Alexis Polux. Polux was suspicious of the calm around the Phall system when everywhere else was fucked as far as the third eye could see and began rigorously drilling and training the men under his command, which turned out to be a very good thing when the fleet of the traitor IVth turn up.