Leman Russ

"'I mean, for Helvete's sake, it looks like you haven't fought or fucked anything for decades, you MILKSOP. Have ye no wolves?!'"Leman Russ is the Primarch of the Space Wolves, and sixth son of the Emperor. He is known as the Emperor's Executioner, and is remembered for the part he played in the Burning of Prospero, earning the undying hatred of Magnus the Red.

Official Canon
Leman Russ was found on the savage ice world of Fenris, where he had originally been raised by Fenrisian Thunderwolves until he was found by the locals. He quickly became King of the planet, until one day a mysterious stranger appeared to challenge Russ to a duel. This being proved to be his true father, The Emperor. Having reunited with him and his legion, Leman Russ took command of the Space Wolves, or as they are known in their language, the Vlka Fenryka. An already untamed legion, the Wolf King made use of Fenrisian lore and local veterans to focus their bloodlust in the right direction.

Great Crusade
During the Great Crusade, Leman Russ gained his reputation as the Emperor's Executioner, punishing non-compliant worlds and oathbreakers with brutal efficiency. And it is heavily implied that he had been involved in the expunging of the two forgotten legions, of which the details are still a secret to this day.

Russ was known for being extremely stubborn like Rogal Dorn, but unlike him he was also quite prideful and short-sighted. Twice he got into avoidable fights with his brothers Lion El'Jonson and Angron. During the Crusade, Leman Russ lead the anti-psyker faction in the Council of Nikea, insisting that psykers were too dangerous to be allowed to use their craft. When pressed about the existence of psykers in his own legion, Leman Russ insisted that his Rune Priests drew their power from the nature spirits of Fenris, not of the Warp.

Horus Heresy
When the Emperor ordered for Magnus the Red to be arrested to be held accountable for breaking into the Imperial Palace, Horus intervened and gave Leman Russ a different set of orders; that Magnus was to be killed and Prospero to be destroyed. Leman Russ accepted the orders without question, and while Magnus and his legion escaped, Prospero was no more.

Following the Horus Heresy, Leman Russ outright refused to accept Roboute Guilliman's Codex Astartes. However, his legion gradually dwindled, as the unstable Space Wolves gene seed meant that they could only recruit from Fenris. Tired of wasting away on their home planet, Russ took the 13th Great Company with him into the Warp to search for Magnus and settle their old score once and for all.

TTS Canon
Leman Russ was discovered by the Inquisition after they had been exiled into the Warp by Magnus the Red. Russ told them that the key to survival is to have supreme confidence in your abilities and the daemons can't touch you. He gets them drunk on a home-brewed liquor made from bylestim and liverjuices of a Bloodthirster, a very potent drink not unlike Fenrisian Ale, then they go on a rampage pulling pranks and slaying many daemons along the way. Russ himself doesn't need the Ale since, as a Primarch, he can easily go toe-to-toe with Daemons, and Kaldor Draigo's insanity has largely inoculated himself against the horrors of the inmaterium.

As Fyodor Karamazov sobered up, he tried to convince Russ to help them escape the warp, claiming that he was in fact a shard of the Emperor's soul. Russ refused to believe him, but upon hearing that Magnus was spotted in the Emperor's throne room, Russ resolved to make a beeline for the Gate of Khaine, one of the few exit points in the Warp located deep within Comorragh. During the battle at Khaine's gate he leads the rag-tag army of survivors, while the psykers accompanying them try to open the gate. When the Star Child combines itself with Fyodor and the latter acquires a strong resemblance to the Emperor, Leman is left stunned, and eventually forced to admit the possibility that Fyodor was a part of his father, even if the idea nauseated him. He also knew that Fyodor would use his new psychic charisma to force everybody to comply with the Dark Eldar's demands, saying that it "will be very painful."

Despite hating psykers, Leman Russ is likely a latent psyker himself, as he was able to conjure the words he was thinking of during his game of 20 questions with the Dark Eldar, using his powers to passively torment his captors to death or to psychologically break them. He is also apparently friends with the dwarf Urist Boatmurdered. Between being able to outwit daemons and out-torment Dark Eldar, Leman Russ demonstrates a sadistic cunning that is rarely acknowledged by his brother Magnus.

Quotes

 * "What in the wolf did you just howlin' say about me you little milk-sop? I'll have you know I was throned the top of my tribe in the kingdom of the Russ and I've been involved in numerous executions of Traitor Primarchs and I have over 300 million confirmed kills. I am trained in wolf warfare- and I am the top CQC expert in all of the Imperium. Ye aren't nothing to me but just another Nancy Lion-Lover BITCH!"
 * " Daemons of Khorne are gonna eat you out like ice cream sandwiches once your red rage begins."
 * "CHUG! CHUG! CHUG! CHUG! CHUG! CHUG!"