If one must find a similarity, it somewhat resembles the divine power of All Gods fused with Divine Nature—Undead Divine Power.
If it indeed were divine power, accomplishing this feat wouldn't be difficult.
But the question is, how could a mortal grasp both Undead Divinity and Undead Divine Power?
Old puzzles were solved, only to extend into more new puzzles.
Blood Horn, vast as it was, lacked a powerful Necromancer like Arms, so neither the Undead nor the Shadow Power could put up any real resistance.
On Gaven's side, there were unique beings like the Six-Armed Snake Demon, Daphne, and Estelle, putting the two sides on completely different levels. Their occupation of Blood Horn was visibly swift—the ash-grey devoured the black.
And as they progressed, they became faster, because they faced the same situation as they had in Efanso City Hall: the victor took everything.