Since the Lifelong Realmlord could govern an entire realm, he naturally had something he can depend on. By merging his Rot Heavenheart Mandate with his Lifelong World Heart, it was able to cause the corrosion energy to be unending, capable of constant regeneration until his opponent corroded completely.
Back then, he depended on his Lifelong Heavenheart Mandate to manifest his world heart. He did this precisely because he wanted the regenerative supporting capabilities.
Boundless corrosion energy continued to invade Qin Wentian's body, destroying it slowly by rotting it away. The lips of the Lifelong Realmlord curled up into a malevolent smile. A genius? Taking just a hundred years to climb from the mid-stage of the immortal emperor realm to the gate before the world overlord realm? So what of it? No matter how strong his talent is, it's nothing at all compared to death. As long as he died, everything would return to the void.