Noah had seized many pieces of the Eternal Snake's body during the battle. He would normally eat those resources to improve his body, but he had a better use for them now.
He had to learn how those tissues functioned to replicate that ability. The Divine Deduction technique never stopped consuming his mental sea in that period to bring him closer to a solution.
All his ideas eventually converged toward an unavoidable decision. He had to involve the Body-inscription spell in the process. The only problem was that he had yet to invent the procedure.
Noah needed to embody the innate ability of the Eternal Snake. Translating it into a spell or technique would make it depend on his darkness and mental energy, and it would also fail to express its real power.
Instead, Noah wanted to add that ability to his bloodline, which meant that he had to modify his body to succeed in that task.
