The Canis Helix is at once the Wolves' greatest strength and their fatal flaw; because the Wolves' geneseed is inherently unstable, the Wolves' first (and possibly last) attempt to create Successor Chapters was a complete disaster. When the Legion was divided after the Horus Heresy, a new chapter, the Wolf Brothers, was created. The Wolf Brothers were intended to be the first of many Successor chapters, but quickly succumbed to the Curse of the Wulfen and scattered. Thereafter, the Wolves all but abandoned their hopes of copying themselves.[2a]
In M32, Thar Ariak Hraldir, the Wolf High Priest of the Space Wolves was conducting experiments, which he called "The Tempering" to control the instability of the Canis Helix, and believed he was close to succeeding.[2b] However, his laboratory was destroyed by Magnus the Red during the Battle of the Fang. Magnus, afraid that the Wolves might succeed in proliferating, made a point of destroying the lab and killing Hraldir before moving on to assault the heart of the fortress.[2c]
The Tempering was a controversial project, and was thus a closely guarded secret within the chapter. It had the approval of Wolf Lord Vaer Greyloc and the Great Wolf, Harek Ironhelm[2d], but the venerable Bjorn, when he learned of the project, was outraged and called it a betrayal of their primarch, Leman Russ; had Magnus not destroyed it, Bjorn said, he would have done so himself.[2e] Even a mortal kaerl of the Wolves, Morek Karekborn, thought the prototype Space Marines he saw in Hraldir's lab looked terribly unnatural and lacking in the feral potency he was used to sensing from the Wolves[2f]. Hraldir also admitted that he had not yet been able to stabilize his test subjects to the point where they could survive on their own, though he believed he was getting close.[2b] It is thus uncertain whether the Tempering would have succeeded even if Hraldir had completed his work.
source: Lexicanum