Eight Greed Kings

Eight Greed Kings (八欲王) are legendary figures in the New World who appeared five hundred years ago and conquered the world with incredible power. However, their rule was short-lived due to an internal conflict which led them to self-destruction. Nowadays, most of the ruins they constructed are destroyed, and the only city left is under their floating castle, Eryuentiu.

Strength
The Eight Greed Kings were known to be extremely powerful, as they have slain most of the Dragon Lords during their battle. They left behind the Eight Great Weapons, including their guild weapon (sword). Ivileye mentioned their item "Nameless Spellbook" is worth the price of a single world, so it may be a World Class Item.

Trivia

 * It is certain that they are YGGDRASIL players, as their city produces items only existed in the Earth, like suit or katana, and they owned a guild weapon.
 * Also, in web novel, it is confirmed that they can revive after death, though they become weaker and weaker repeating the revival. It might be due to the revival penalty of YGGDRASIL.
 * It's said that if the Eight Greed Kings didn't try to dominate the world, humanity would have already been eliminated by the stronger races.
 * Brain Unglaus got his katana from their city.