Underworld

The Underworld is a massive underground kingdom/region in the universe of Ousama Ranking. It is ruled by King Desher, the #2 ranked king in the world.

Entrance
The only official route into the Underworld is the perilous Gates of Hell, a massive sinkhole which erupts in enormous gouts of flame periodically, intimidating any who would visit. There is a hidden staircase spiraling down the sides of the sinkhole, which is notoriously difficult to traverse, filled with cursed mists that will kill the average person if they attempt to enter.

The Bosse Kingdom has created a separate entrance to the Underworld beneath their capital city. This entrance is unknown to most and definitely unapproved, if not outright illegal.

King Desher
Ranked #2 in the world, Desher is an exceptionally powerful king who possesses some supernatural powers.

Desper
King Desher's younger brother, Desper has the supernatural power to sense hidden abilities in other people. He has a poor relationship with Desher. Desper is acquainted with Bebin, and has agreed to train Prince Bojji to bring out his hidden abilities.

Knights of the Underworld
A famous chivalric order that serves King Desher, it is dedicated to protecting the overworld from the dangerous creatures of the Underworld. The Knights of the Underworld are shown to be relentless and merciless, going so far as to hunt peaceful monsters for years after they've escaped to the overworld.

Ouken
Ouken is the disgraced former Commander of the Knights of the Underworld. He was imprisioned by King Desher until being freed by Miranjo. He is such a fierce swordsman that he's known as the Sword King of the Underworld.

Monsters & Demons
The Underworld is the natural habitat to many monsters and demons. Some are capable of speech and reason, and live alongside the humans in Desher's kingdom. Others are closer to to wild animals, but it's unclear where they live in relation to the human kingdom.

It appears that the Underworld does not allow intelligent monsters or demons to migrate to the overworld, and punishes attempted border-crossings with death.