Towards the end of the Age of Strife, the Emperor crafted 20 magical clone babies that he called Primarchs. The forces of Chaos didn’t like the Emperor very much, so they kidnapped his magical clone babies and threw them randomly all over the galaxy, and the Emperor had all kinds of adventures finding them again. This thread is about the 9th magical clone baby the Emperor recovered – Magnus the Red, Primarch of the 15th Legion.
Magnus crash-landed on the world Prospero, a dark and desolate world, settled by psykers who had fled persecution all over the galaxy, chosen because it was really goddamn far away from Earth. This was lucky for Magnus, because was ALSO a psyker, whose psychic powers were rivaled only by his Father. He got all kinds of training in utilizing his psychic powers and in perceiving and manipulating the Warp, the dimension from which all psychic powers (and Chaos) came.
Magnus is a good example of why we should always take the stories of the Magical Clone Babies with a grain of salt. Because his name was Magnus the Red, he is regularly depicted as having unnaturally red skin. Because he sacrificed one eye in an ill-considered deal with the Chaos God Tzeentch to save his space marines, he is depicted as being a cyclops, with one big ol’ eye in the middle of his forehead.
The giant nipple horns are historically accurate, though.
Magnus also has a reputation for being a massive failson. See, when Horus got all infested with Chaos, Magnus said, “I gotta tell Dad!” – because of warp storms, astral telepathy was blocked, so Magnus tried astral projection. He zoomed back to Earth, but the Emperor seemed to be stuck inside of some kind of weird tunnel. Magnus pounded and pounded on the tunnel until he broke through – this unleashed chaos daemons into the secret tunnel that the Emperor had been digging into the Eldar webway. The Emperor was not pleased.
The Emperor sent Magnus’s brother Leman Russ to punish Magnus for this fuck up. When Russ arrived, he orbital bombarded the sole city on Prospero into rubble, Magnus finally had enough of this crap and used his psychic magic to transport the survivors of the city, all of his space marines, and everything else that he loved to the mysterious Planet of Sorcerers, deep in the Eye of Terror. From there, he coordinated his Space Marines as they fought against the Imperium that did them dirty.
These days, Magnus spends most of his time trying to reintegrate all the shards of his soul that had been broken and scattered throughout the warp by Tzeentch when Magnus made the mistake of asking for a second favor. His space marines have all been magically turned to dust and sealed inside their power armor. Prospero has been destroyed. Poor Magnus, he was only ever good at one thing, and his dad decided that one thing was evil.