Rogal Dorn

Turn to the side and cough...

Rogal Dorn is the Primarch of the Imperial Fists Chapter, which was a Legion before Horus fucked everything up.

The Imperial Fists are quite famous for fortifying the shit out of everything and INTENSE CAMPING which pisses off every other race. They are highly likely the reason that The Emprah didn't get raped by Horus during a certain (totally awesome) siege. His evil twin/Brother is Perturabo, Primarch of the Iron Warriors, who turned to Chaos because he was one of Horus's ass slaves. As Perturabo constantly fucks up all of Rogal's shit, Rogal has developed a special kind of rage towards him.

When the Emprah totally fucked up Horus, Rogal seemingly came out of nowhere and saved his ass, then got all pissy about it because he was only a few seconds short. Surprisingly, he did not turn into an Angry Marine, but still whines about it like some emo bitch who can't move on. Much later after the Second Founding, he declared to everyone that he'll capture his nemesis, Perturabo inside a metal cage. Pert then trolled Dorn by setting up the "Eternal Fortress", which was fortification after fortification that led into a fortress that Perturabo was residing in. It took the Imperial Fists three weeks to wade through the shit Perturabo set up. However, it was too late for Dorn to realize that he has just been trolled by Pert. When his Imperial Fist strike force reached the actual fortress, it was actually empty with the Iron Warriors waiting in ambush. The Imperial Fists then got their asses handed to them, up until the Ultrasmurfs came in and rescued them.

Somewhere along the line, Rogal got in a big-ass ship and got pwned by Angron in the first Black Crusade, therefore proving that RAEG ends all things and how Angron is the only Chaos Primarch that gets anything done these days.