Dungeon Life - Chapter Eighteen: Secret Base

Amid the silence of the aftermath, a sealed envelope was found resting beside the fallen Infinity Blade. Its edges were worn, as though it had been carried for many years, yet the seal remained intact. Gok, known for his stoicism and strength, had written it long before the final battle, anticipating that one day his journey would reach its end.

Ham Dani, a normal student whose hobbies were to read novels.

The world that nurtured the civilization which reached the pinnacle of magic was on the verge of destruction.
The last survivor transmigrated to the past, when the magic civilization started growing, as countless mages were still fumbling their ways through the thorny paths of magic knowledge.
He, who came from the end of the magic era, aim to reach the pinnacle of magic.

- Description from Novelupdates

The era of mutations and survival!Can Jeremy Night become the hope of the Human Alliance?