Indeed, the reason Greg Jensen wore it down in a drawn-out battle instead of eliminating it directly was to gain full control over it.
On one hand, if a Level Nine Ferocious Beast could be tamed, it could become a powerful ally in his corner, and once its strengths were maximally utilized, its use might surpass that of the Three-eyed Golden Eagle.
On the other hand, this creature must have come from Shadow Province; it presumably knows the true identity of the Beast King lurking behind the scenes, and perhaps Greg could obtain more useful information from it.
After the control of the Blood God Pact, the one-horned King of Corpses indeed became much more obedient and provided an answer:
"There's a Level Eleven Lion King on the savannahs of Shadow Province, with strength that defies the heavens, and it holds us all in its grip!
