Magnus the Red
Magnus the Red is the primarch of the thousand sons, and rules over the planet of the sorcerers.
Magnus landed on the planet of prospero (A planet who's ancient civilisation were composed predominantly of psykers, until they were royaly fucked over, almost into extinction, by native predators that layed their eggs into a psykers brain.). He quickly mastered all they've taught him and became their ruler.
He was renuited with the Emperor and saved his legion (Who were suffering from the flesh change) by bargaining, unknowingly, to Tzeentch. After a few years of rebuilding their numbers, they joined the great crusade. Unlike the majority of the other legions, Magnus focused more on diplomacy and cunning planning into order to bring worlds into compliance.
Magnus and his legion were always the target for controversy. The main prosecutors were Mortarion, Rogal Dorn,Corax and recently Lemun Russ. When one of their Captains suffered from the flesh change, they were called to stand trial. The Emperor deemed that sorcery is to be banned. Magnus didnt like this, so he feigned modesty and complied, when in reality, he and his legion continued to practice sorcery.
When Magnus learned of Horus' treachery, he attempted to warn the Emperor. But the Emperor didn't listen to him (And paid for it) but the Emporor already new of the treachery and was planning against it, with a super powered Horus killing death machine!!!!! but because Magnus used 'BANNED' sorcery to warn the 'big cheese' he unwittingly destroyed said SPHKDM which completly fucked over the imperium and all Empsy did was shake his head uttering "son i am dissapoint" and send Lemun Russ to bring Magnus back to Terra. Horus used this situation to his Advantage ordered Russ to, instead, destroy Magnus.
So the Space wolves,adeptus custodes,sisters of silence and a million of imperial soldiers attacked Prospero. Magnus and his legion escaped to the Planet of the Sorcerers. He then joined Horus during the siege of terra. Horus lost, and Magnus retreated back to the planet of the Sorcerers.
Continue please...