Demons

Demons are a race of sentient creatures that originate from the Underworld and once inhabited the human world.

Background
Demons once inhabited the human world and only came out at night, which is when humans would sleep. The cycle where humans rise at dawn and demons rise at dusk continued for centuries before being broken by artificial lighting. After the invention of lightbulbs, humans took over the night, resulting in demons furiously rebelling by attacking humans and the formation of the Department of Night that protects humans from demons. Before the year 1860, two demon lords were born in the Underworld, who were Xi Sha and Che Yongtai's previous incarnations. Xi Sha's previous incarnation conquered and ruled over the Underworld while Che Yongtai's previous incarnation attempted to conquer the human world. The two eventually met their demise after humans and demons cooperated and defeated them at the cost of countless warriors. After centuries of conflict, the rocky relationship between humans and demons was finally resolved when the secretary of the Department of Night, Wang Shengli secretly formed a truce with the leader of the Underworld, Yan Wen, prohibiting demons that are under her control from attacking humans. Consequently, some demons decided to return to the Underworld, while others learned to disguise themselves as humans and remained in the human world.

Characteristics
A common trait among most demons is that they all possess orange-red skin and incredibly long lifespans. However, due to the multitude of different demon races that exist, each demon possesses physical traits unique to their own race.
 * Demon Lords (魔王): Demon lords, despite appearing humanoid, are a unique race of demons that are vastly superior in terms of power when compared to other demons. A common physical trait shared by demon lords is that they all possess horns similar to those of bulls, though female demon lords naturally lose their horns after their sexual awakening, and long hair will immediately sprout out of the location of the horns. Demon lords also possess abnormal strength, endurance, stamina, and senses, as well as the ability to detect an organism's age by looking at them, and the ability to regenerate new organs if removed. Demon lords are able to reproduce sexually and asexually, they are also oviparous, and are capable of reincarnating and nurturing themselves. These diverse methods of reproduction result in demon lords not having any stable blood relationships, and consequently, lack of knowledge about kinship.
 * Power King Clan (力王族): One of the Four Imperial Guard Clans serving under Yan Wen. Demons from the Power King Clan appear humanoid. They possess large muscles and have pointed ears. Judging from their name and the new generation's Power King demon's display, this race of demons seem to excel in strength and physical power.
 * Iron Hoof Clan (铁蹄族): One of the Four Imperial Guard Clans serving under Yan Wen. Demons from the Iron Hoof Clan resembles deers in appearance, though they possess sharp teeth. They also possess hooves, pointed ears, a deer-like facial structure, and a horn protruding out of their foreheads that indicate their age. Older demons have longer horns while younger demons have short horns. Judging from their name and the new generation's Iron Hoof demon's display, this race of demons seem to excel in leg strength and kicking power.
 * Sky Slash Clan (断空族): One of the Four Imperial Guard Clans serving under Yan Wen. Demons from the Sky Slash Clan appear humanoid. It seems to be a tradition for members of this clan to wrap their head in cloth, revealing only their eyes, and wear a long scarf that wraps around their neck and right shoulder. Sky Slash demons also grow large wings sometime after the age of twenty. Judging from the new generation's Sky Slash demon's display, this race of demons seem to excel in swordsmanship.
 * Elder Clan (长老族): One of the Four Imperial Guard Clans serving under Yan Wen. Demons from the Elder Clan appear humanoid. They seem to prefer wearing large cloaks with shoulderguards that cover their entire body. They possess two horns that grow on each side of their head, and pointed ears. Male members grow spikes under their chin that resemble human facial hair when they become older. Judging from the new generation's Elder demon's display, this race of demons seem to excel in magic attacks.
 * Luoying Clan (罗影族): Luoying Demons appear humanoid, and all possess a single purple horn that protrudes out of their foreheads. Additionally, they all possess pointed ears. Luoying Demons are able to revitalize their bodies when it grows too old through the use of the "Hibernation Reincarnation" technique, which allows them to achieve immortality, and accumulate memories of relationships and psychological knowledge while losing memories relating to combat.
 * Luoren Clan (罗刃族): Luoren Demons appear humanoid, and all possess two purple horns that protrude out of their foreheads. Additionally, they all possess pointed ears. Luoren Demons are able to revitalize their bodies when it grows too old through the use of the "Hibernation Reincarnation" technique, which allows them to achieve immortality, and accumulate memories of assassination techniques while losing memories of relationships and emotions.
 * Transmit Clan (传音家族): Transmit Demons all possess horns that protrude out of their heads. Males have two horns while females have one. All Transmit Demons possess the technique "Telepathy Link", which allows them to telepathically communicate with those they established a link for five days, even if they are located in a different dimensional plane.

Members

 * Yan Wen: Ruler of the Underworld. Most of the Underworld is under her control. Very few races of demons aren't governed by her.
 * Left-hand Man: One of the two high-ranking assistants to Yan Wen.
 * Right-hand Man: One of the two high-ranking assistants to Yan Wen.
 * Che Yongtai: Reincarnation of one of the two demon lords that massacred countless humans and demons in the past.
 * Xi Sha: Reincarnation of one of the two demon lords that massacred countless humans and demons in the past.
 * Crimson Blood (deceased): An arrogant demon general serving under Yan Wen who was killed by Che Yongtai after attacking him.
 * Black Water (deceased): An arrogant demon general serving under Yan Wen who was eaten by Xi Sha after attacking her.
 * Xiao Jian: A demon who is acting as a spy for the Underworld and servant for the two demon lords currently.
 * Pearl: A demon born with the rare ability to reattach her severed limbs, who eventually left for the human world.
 * Deng Yuankui's butler: A demon who serves as the butler under Deng Yuankui and his wife An Ningxue.
 * Shi Ji (deceased): The strongest spy from the Luoying Demons. Eventually left for the human world during the Warring Period and became one of Che Yongtai's previous incarnation's concubines. Later returned to the Underworld to steal the Heaven Crystal fragment from Yan Wen.
 * Jian Tong: The strongest assassin from the Luoren Demons. Eventually left for the human world during the Warring Period and remained there.
 * Jack: A member of the Transmit Demons and lover of Rose.
 * Rose: A member of the Transmit Demons and lover of Jack.
 * Public Relations Specialist (deceased): The current generation's public relations specialist for the Underworld.
 * Champion (deceased): The champion of the Underworld wrestling contest that happened a year before his appearance.
 * Y'Shari: King of Qin'guang Valley and previous co-ruler of the Underworld. Xi Sha's previous incarnation's lover.

Demon races
Four Imperial Guard Clans: Four races of demons that serve under and protect Yan Wen. Consists of the Power King Clan, the Iron Hoof Clan, the Sky Slash Clan and the Elder Clan. The younger generation of these clans were all killed within the Limbo Stone dimension created by Shi Ji.

Luoying Clan: A race of demons that are natural-born spies. Conducted multiple espionages during the Warring Period in the human world.

Luoren Clan: A race of demons that are natural-born assassins. Conducted multiple assassinations during the Warring Period in the human world.

Transmit Clan: A race of demons that are born with the unique ability "Telepathy Link".