The Dungeon’s Last Master

A teenage boy named Eli Broom is trapped inside a manhwa-style dungeon for ten years by a mysterious condition that prevents him from leaving. He never ages, gradually levels up, and develops an alter ego: the Phantom Stag, a reclusive master wearing a stag mask that symbolizes his speed and agility, plus a cloak. Meanwhile, the entire world undergoes a massive webtoon-style event that causes portals to appear everywhere. The outside world sees the masked master as a legend because he trained five disciples who went on to become legends. Now Eli can finally escape, but a portal-filled modern world may be less safe than the dungeon.