The Alchemist's Bargain [REWRITTEN, link in blurb]

This story has been rewritten and you can find it here https://www.royalroad.com/fiction/154836/engineer-of-ruin-isekai-progression I am keeping this one up for now, for people who might have started this version and want to finish, but take it from me, the new one is better and starts to diverge strongly around chapter 30 :) On the happiest day of his life, David died. Being brought back might be the second cruelest thing that ever happened to him. In his new life he’d love to take it slow and pick apart the rules behind magic. Unfortunately, the world doesn’t care to wait. Each month, an eclipse brings tides of monsters that leave countless dead in their wake. Among the carnage, he discovers a strange, unreliable power: the ability to absorb memories of the freshly dead. "I won! Why don't I feel like it!?" In a world where friend and foe look alike, David will have to find people worth trusting. He will do anything to keep them alive, even if saving one life means destroying a dozen. What to expect from this story: * Weak-to-strong MC * Multiple varied settings: from a poor village to a fortress-city to the wilds * Grimdark world * Multiple sides to every conflict * Extensive and in-depth magic system * Realistic characters * Morally grey MC