The King of Hell pretends to help the Demon Lord reincarnate and cultivate anew, but instead casts his soul into the Beast Realm, forcing him to offer up his sect's supreme treasure, the Myriad Demons Blood Codex, in exchange for freedom.
He feigns submission while secretly gathering the resentment of the King of Hell's 365 concubines to forge the Myriad Soul Needles.
His life as a reincarnated human goes smoothly.
When the demonic cultivators and imperial weapons storm the underworld, he sacrifices himself to detonate that resentment, grievously wounding the King of Hell's primordial spirit. With his dying breath, he roars, “Three hundred and sixty-five blood debts, repaid in full today!”