The story follows Spencer, an orphaned weakling who is forcefully conscripted into the military of the Dragonlands—a world torn apart by the global Dungeon Wars. He has no talent, no physical strength, and is considered expendable by his squad. However, after a near-death experience inside an S-rank Dungeon, he gains an unknown power that allows him to defy the limits of human growth, setting him on a path to become the strongest soldier in history.

Yeah, so, a bit of an older one that I found in my Google Drive, I thought it was cool so I'm posting it.
Bare in mind that there might some discrepancies here and there with the show, but I wasn't as knowledgeable with the show yet.