In Solo Leveling, dungeons serve as a connection between the human world and an alternate dimension that is inhabited by magic beasts.
Ten years ago, tunnels connecting the human world to an alternate dimension started appearing around the world. These tunnels are known as gates.
On the other side of these gates are dungeons, where creatures known as magic beasts are found.
It is the job of the hunters, humans who have awakened special powers, to enter the dungeons and fight the magic beasts.
It takes seven days for a gate to open all the way. Hunters must enter the dungeon during that time and fight magic beasts that cannot be defeated using conventional weapons.
All the magic beasts in a dungeon have a boss. Once the dungeon boss is defeated, the dungeon closes by itself after an hour.
If the boss is not defeated in the first seven days, the gate opens completely, and this event is referred to as a dungeon break.
Once a dungeon break occurs, the magic beasts inside the dungeon can enter the human world and wreak havoc.
Dungeons are places where valuable resources like essence stones and mana crystals are found. These precious stones and crystals can be sold at high prices.
Hunters gather these stones by defeating magic beasts and sell them as a means of earning a living.
Like hunters, dungeons are also ranked. Hunters are sent to dungeons according to their ranks. The higher the rank of a dungeon, the more dangerous the magic beasts within it are.
There are times when hunters encounter magic beasts in dungeons that inspire absolute despair.
When Sung Jinwoo, the protagonist, goes on a dungeon raid, his group kills the dungeon boss, but there are no signs of the dungeon closing.
The group then finds a dungeon within the dungeon. Entering the second dungeon proves to be a mistake, as they encounter a beast that is far too powerful for them.
The group stands no chance of defeating the boss, and most of the hunters do not leave this high-level dungeon alive.