Magnus the Red

Primarch of the Thousand Sons and Daemon Prince of Tzeentch.

Magnus the Red is the primarch of the Thousand Sons, the XV Legion of Space Marines, and a Daemon Prince of the Chaos God Tzeentch. In the early years of the Imperium he was also known as the Crimson King and the Red Cyclops. A copper-skinned giant with enormous psychic power, he spent his life trying to understand and master the Warp; his reckless use of that power cost him the trust of the Emperor and of most of his brother primarchs, and in the end delivered him and his Legion to Tzeentch.

Quick Facts

Legion: Thousand Sons (XV Legion)
Homeworld: Prospero
Patron: Tzeentch
Also called: Crimson King, Red Cyclops

Facts from the source article.

Prospero

When the infant primarchs were scattered across the galaxy, Magnus's capsule came down in the central plaza of Tizca, the only city of note on Prospero, a remote world settled by psykers who were shunned and persecuted elsewhere. Raised by its scholars, he outstripped his teacher Amon within a few years, led a campaign against the psychic predators called the Psychneuein, united the planet's squabbling cults of sorcerers and rebuilt Tizca as the City of Light, with a great library at its centre. Ignoring Amon's warnings, he made long psychic journeys deep into the Warp.

The Emperor and the Thousand Sons

The Emperor's fleet reached Prospero in 840.M30, and he and Magnus greeted each other as if they had long known one another. The XV Legion had inherited Magnus's psychic gifts through its gene-seed, but also an unstable mutation, the Flesh Change, that left its survival in doubt. Magnus stopped the mutations and lost his right eye in the effort; he did not understand that the Warp entities he had dealt with were part of a deception by Tzeentch. About a century after the Great Crusade began, the Thousand Sons joined it as the 28th Expeditionary Fleet.

The Great Crusade and Nikaea

On campaign Magnus gathered sorcerous lore from the worlds he brought into the Imperium and compiled it into the Book of Magnus. His use of the Warp made him suspect to other primarchs, above all Leman Russ of the Space Wolves and Mortarion of the Death Guard; one quarrel with Russ was stopped only by Lorgar. At the Council of Nikaea Magnus argued for psykers, but the Emperor banned the Legions from using psychic powers and disbanded their Librariums. Magnus accepted the ruling unwillingly and soon looked for ways around it.

Magnus's Folly and the Fall of Prospero

After Horus was made Warmaster, Magnus foresaw his corruption and the civil war to come. To warn the Emperor he sent his spirit to Terra by sorcery, accepting help from a Warp entity to break through the Webway; his arrival breached the wards of the Imperial Palace and wrecked the Emperor's secret Webway project. The Emperor ordered Leman Russ to bring Magnus to Terra, but Horus turned the order into one to destroy the Thousand Sons. Knowing by then that he had been Tzeentch's pawn, Magnus left Prospero unwarned and undefended. The planet was bombarded and Tizca stormed; Magnus finally fought Russ, who blinded him and broke his back over his knee. To save his Legion and its knowledge he swore himself to Tzeentch, who carried Tizca and the Thousand Sons into the Eye of Terror.

After the Heresy

As a Daemon Primarch, Magnus rules from the Tower of the Cyclops on the Planet of the Sorcerers, a daemon world in the Eye of Terror. When his adviser Ahriman and a cabal of sorcerers cast the Rubric to stop the Legion's returning mutations, the Legion's non-psyker Astartes were reduced to ash, their spirits sealed inside their armour; Magnus defeated Ahriman and exiled him. In the 32nd Millennium he attacked the Space Wolves' fortress, the Fang, killed the Great Wolf Harek Ironhelm and destroyed the gene-laboratories meant to create Space Wolf successor Chapters. In 999.M41 he led the Siege of the Fenris System; Logan Grimnar banished him with the Axe of Morkai, but Magnus used the deaths on the world of Midgardia to move the Planet of the Sorcerers into orbit over the ruins of Prospero. In the Era Indomitus he offers psykers a refuge there, on the world called Sortiarius.