[Supreme Wars: Act III] 5/9: The Realm Devourer!
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The Necrotic Plane Ruler had laid off his plan perfectly, utilizing Hel as a connection to Helheim's tremendously big Realm Core, he managed to imbue most of his Soul into it, turning it into his vessel, and by using this core's powers plus his own, he stealthily, and below everyone's noses, created a brand new, physical vessel of his own dominion, which didn't belonged to any other soul than his!
Pretty much, it was like a second body, and it wasn't at all like just possessing someone else. Indeed, he had struggled a lot, but he managed to buy enough time, when Zehe cut his connection with Hel, it was already too late anyways… This entire Realm became his second body.