Outside is Apocalypse But I am Safe inside My Dungeon

That day when the apocalypse fell, was a normal day without any big events. like any other, people are busy in their lives and work, some enjoying their lives some are struggling to live. Life was going in a usual routine until changes in the earth started to show up on the surface. while they were living a normal life, the earth was undergone a massive transformation without being noticed. Mysterious energy started to leak from the underground and living or non-living beings that were exposed to this energy began to evolve. Zombie and mutant beasts are roaming in the City. Due to large numbers and sudden appearance, armies from all over the world fail to withstand their attack. Big cities became a playground for savage beasts. Following those events, another catastrophe came that forced humanity to its knees. The environment of Earth has turned into a mess, green lands have turned into deserts and heavy rainfall causes river overflow. the length of winters increased and it has become very harsh for a normal human to survive. Food and shelter became scarce objects that very few people could afford. Instead of fighting mutant beasts and zombies, humans started to kill each other for easy resources. In this world, a piece of bread is more precious than a human life. This is where the story begins, in this horrible world, Sam is the only person who has a safe place with warm meals and every need that people could only imagine. Sam's life was always not that good, at a young age he lost his parents and the people he trusted most betrayed him. He fell into a debt trap that was impossible to escape. But Everything changed after he received his ability as a dungeon lord. At a young age, he faced many hardships and spent all his time working which is why Sam decided to lead a relaxed and enjoyable life even in the apocalypse.