Ulrik the Slayer, also known as Grandfather Lupus and the Guardian of the Sons of Russ, is the Wolf High Priest of the Space Wolves Space Marine Chapter and is the oldest of all the Space Wolves other than the Chapter's Dreadnoughts. His great mane is white as the slopes of Asaheim on the Space Wolves' Chapter homeworld of Fenris. Ulrik is older even than the mighty Logan Grimnar, the Great Wolf of the Chapter, who has fought in the name of the Emperor for over 700 Terran years.
In his long career Ulrik has fought in countless battles, winning honour for his Chapter again and again. It was during the First War for Armageddon that Ulrik first won renown fighting in the Wolf Guard of Lord Kruger's Great Company. Kruger and his men stormed into invading companies of World Eaters, meeting the bloodthirsty Traitors with equal fury, for the fruit of betrayal is terrible wrath. Kruger himself was cut down and, though Ulrik had lost his own blade in the desperate close-quarter battle, he leapt to defend his dying Wolf Lord, killing three hulking World Eater Khornate Berserkers who had laid Kruger low in the bloody melee. Ulrik fought like a man possessed -- the spirit of the Thunderwolf was strong in him that day, inspiring his Battle-Brothers and even earning the unusual accolade of a grim salute from Angron, the Daemon Prince of the World Eaters himself. The Imperium eventually emerged victorious. Ulrik earned the accolade "the Slayer" from that day forth, and was elected by his fellow Wolf Guard as Kruger's replacement at the head of the Great Company. He declined the honour, which was all but unheard of, instead preferring to fight alongside his fellow Space Wolves rather than lead them. Ulrik chose to become a Wolf Priest instead, and in the long years since his investiture he has earned perhaps his greatest accolades by selecting and training many of the Chapter's greatest warriors.
Before a century had passed, it had become obvious that Ulrik's true genius was in the selection and training of new recruits. He was a veteran of so many wars that his tactical and martial knowledge was invaluable, and his natural charisma made him an excellent mentor. In recent years, however, Ulrik has become ever more aggressive on the battlefield, swearing great oaths to cut down the most deadly of enemies in the name of the Emperor without a care for his own safety. His combination of near-unmatched experience and natural ferocity makes Ulrik a truly deadly warrior, and those who fight alongside him are buoyed up by his natural charisma and excellent mentoring ability.
It is Ulrik's sacred duty as a Wolf Priest to recruit and train new Aspirants for the Space Wolves Chapter. In his time, Ulrik has chosen and trained a great many of the Chapter's luminaries and greatest heroes. In fact, Ulrik is the only living Space Wolf who remembers the Great Wolf Logan Grimnar as a young, impetuous Blood Claw, full of fury and future promise. Ulrik witnessed this youth marked by the spirit of Russ rise to glory, and accompanied him during many of his greatest exploits, forging a friendship bound by chains of honor and loyalty stronger than tempered steel. Indeed, Ulrik is the only Space Wolf who still addresses the Great Wolf by his first name.
Ulrik embodies the sacred duty of the Space Wolves to protect the innocent from the monstrous enemies of the Imperium of Man. The indomitable Wolf Priest leads his charges in a great solemn oath to hunt and kill fearsome xenos monsters and the mighty warlords of Chaos wherever he finds them.
As High Priest of his order, Ulrik has been gifted the sacred Wolf Helm of Russ, said to have once been worn by the Primarch of the Space Wolves himself. This is both a potent symbol of the Chapter's honour and an arcane artefact that instills fear in those under his gaze. When he goes to war, Ulrik the Slayer is a terrifying foe indeed, resplendent in his black Power Armour, the Wolf Helm and wielding the crackling Crozius Arcanum that act as his badge of office.
- Codex Space Wolves (5th Edition), p. 50