Battle of Phall
The Battle of Phall is one of the biggest space battle of the entire Horus Heresy and, given that it 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.
On team Horus we have Perturabo, Primarch of the Iron Warriors and his war fleet.
The coming of the storm
En route to the Istvaan system, since Rogal Dorn heard about Horus' plan to crash the Imperium with no survivors, the Retribution fleet was forced away from the Raven Guard, Iron Hands and Salamanders and marooned them 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.