That world is a damp planet lit only by a magical green moon. There, its people (who consist of zombies) emerge fully-formed from magical graves, and they “die” by vanishing into a flash of light to be reincarnated. Its zombie-people exist to suffer: they celebrate their own unlife and fear “birth”, or the time when they disappear. As every zombie can reappear and reemerge from the nearest grave after their body is completely destroyed, many popular sports in that world tend to consist of very cruel forms of combat.
It is also home to deadly forests and large, glowing mushrooms, out of which emerge wolf-like beasts and great spiders that feast on anyone unfortunate enough to wander into them. It is also inhabited by unintelligent, cannibalistic vampires who either prey on anyone who enters the forest, each other, and the mushrooms.
This world of Yam Gaai was created by the third king of the underworld, Cho Giongwong (楚江王), as his personal experiment. Although it was protected by a system of magical barriers, occasionally a demon would sneak past the barrier and wreak havoc on that world, burning large areas of that planet with its hellfire.