User blog comment:DirgeOfCerberus111/Space Wolves Successors: Canon or Not?/@comment-3258762-20121105072829/@comment-9734625-20121105172405

If reason number 3 is false, then all it would require is that the geneseed is implanted into a person from a really harsh world, say, Northag, for instance(It is essentially a huge iceball with huge sabretooth lynx, giant wolly mammoths, enormous hawk-like creatures and orcas the size of whale sharks. Did I mention it is a planet-sized iceball, with frequent snow storms?), for the implant to work. The only reason that SW Geneseed is SW exclusive, is that Russ left a psychic imprint on the Fenrisians, and as you said yourself, that might be untrue. If we look on the prooven facts that you have provided here, we only need someone from a world incredibly alike Fenris.