Space Wolves are the most unique Space Marines
When looking for an Army to collect in Warhammer 40,000, the Space Marines are mostly uniform in their overall nature, but one Chapter that is starkly unique is the Space Wolves, who possess an anti-authoritarian viewpoint that presents a completely different command structure and troop variety. The chapter’s gene seed is corrupted with a defective gene called the Mark of the Wulfen which is a result of the Primarch, Leman Russ.
Russ is one of the twenty Primarchs of the Emperor which were created from His very own essence to lead the Adeptus Astartes on the Great Crusade of Humanity. He was fierce in battle and very strategically cunning, but also slightly unhinged partially because of his genetic defect. He was staunchly loyal to the Emperor, though he at first denied Him. When ordered to destroy Magnus the Red and his legion The Thousand Sons, he decimated a large part of the heretical forces, but Magnus and the surviving marines retreated into the Eye of Terror, where chaos has consumed physical space.
After the Horus Heresy, Russ held an enormous feast and after which he gave a speech announcing he was leaving and would return before the final battle. He disappeared, and rumors are that he is hunting Chaos forces in the Eye of Terror. He also ordered a group of Marines to join him, called the Thirteenth Great Company. They have fought in the Eye for ten thousand years, and are so few they are forced to deploy even the most horribly disfigured wulfen soldiers. The wolf packs act as shock troops that rush into the melee with their claws and teeth, completely overtaken by their feral nature. The Space Wolves are specialized in assaulting the enemy and overtaking them in ferocious melee combat, and while the Mark of the Wulfen makes the warriors unstable, they are staunchly loyal to the Emperor and immensely powerful thanks to their power armor. If you would like to learn more about the wolves or even buy a Space Wolves Codex, go to Greyarmored.com.