Curse to Steal the Way

After the undead natural disaster, I became the only death warlock in the world, but the god who saved me made my body full of mushrooms. The curse owner said this was a gift, transplanting a "heart" for me and teaching me to feel fear and love. But when this heart started beating, what I heard was thousands of dead souls wailing in it - it turned out that I was the living key they used to open the "divine way". Now, the false god wants to kill me, the Beast King is watching the game, and the remains of the real god are sleeping in the city beneath my feet. Well, then use the trembling heart you have given me to control the final death.