Digimon Sovereigns

The Sovereigns are a group of fictional characters that appear in the anime series, Digimon: Digital Monsters. There are four, Azulongmon (Qinglongmon), Zhuqiaomon, Baihumon, and Ebonwumon (Xuanwumon). There is another, final member, named Fanglongmon (Huanlongmon).

In Japan, the group's name is Shiseijuu, or Four Holy Beasts.

Name Origins
The Sovereigns are portrayaed as ruling over a quarter of the Digital World. This ties into the mythological figures that they are all based off of, which are all based on Chinese astronomy. In Chinese, the four quadrants of the sky (east, west, north, and south) are known as Celestial Temples, and are individually called Qinglong, Zhu Que, Bai-hu, and Xuanwu. Qinglong means "Blue Dragon," Zhu Que means "Red Bird," Bai-hu means "White Tiger," and Xuanwu means "Black Tortiose."

The Japanese based the Four Gods of Kyoto on the Chinese Ssu Ling, deriving the names Seiryu, Suzaku, Byakko, and Genbu from them.

In the dub, Qinglongmon was changed to Azulongmon and Xuanwumon to Ebonwumon, but the names essentially mean the same as their Japanese incarnations.

Fanglongmon is based off of the Yinglong, the Yellow dragon, and Huang Di, the Yellow Emperor. Or it's possible that he's based on the general Chinese Dragon.

Digimon Adventure 02
In this series, the dub refers to the group as the Harmonious Ones.

The Harmonious Ones are the guardians of the four compass points of the Digital World. Azulongmon is the guardian of the Eastern region, where the Japanese DigiDestined's adventures take place (corresponding to the real world location of the human partners).

In this series, all four Harmonious Ones were defeated by the Dark Masters. After those Digimon were defeated, they hoped to use the power of the DigiDestined's Crests to free themselves. However, when the Crest power was unleashed, they were still imprisoned thanks to the influence of the Control Spires. In anticipation, they created a force to defeat Ken Ichijouji, the Digimon Emperor, by creating the D-3 Digivice, selecting various Digimon, and sealing them underneath the Digi-Eggs. In addition, they transformed the Crest of Kindness, which would later be found by Ken himself.

Later, Azulongmon would drive BlackWarGreymon to destroy the Destiny Stones (Holy Stones), which kept him imprisoned. Ultimately, Azulongmon would be freed when the Digi-Destined themselves used their D-3's to move it, and he revealed himself. After dispatching BlackWarGreymon, he passed on knowledge of the past to the DigiDestined, and left.

Later, Azulongmon would grant a boon to the DigiDestined, by giving them one of the sources of his power, a DigiCore. It temporarily allowed the original DigiDestined to Digivolve into Ultimate again, and for Paildramon to Mega Digivolve into Imperialdramon. Later, Azulongmon would give Tai and Agumon more power, allowing Agumon to become WarGreymon once again.

The other three were not seen in the show. In one of the Audio CD Dramas, Gennai admitted that he did know any of them besides Azulongmon.

Digimon Adventure 02: Tag Tamers
In this game, which serves as a prelude to Adventure 02, the four Harmonious Ones draw Ryo Akiyama into the Digital World, and organize a tournament under false pretenses, so that Ryo may grow in power enough to defeat Millenniumon. However, how they managed to do so while they were supposed to have been trapped is unexplained, so it falls into the realm of a plothole.

Digimon Tamers
The four Sovereigns played an important role in Digimon Tamers. Here, the most prominent is Zhuqiaomon, but unlike Season 2, all four make an appearance.

The Digimon Sovereigns live on the 6th, highest plain of the Digital World, along with the Catalyst, or Shining Digivolution. They were some of the first Digimon to reach their highest form, and in an attempt to distance themselves from humans, they ironically took the appearance of the humans' gods.

When the D-Reaper began to re-emerge, the four Sovereigns could not agree on a strategy. Zhuqiaomon believed that they should use the Shining Digivolution to allow Digimon to digivolve and fight back, while Azulongmon believed that it was the Digimon's ability to grow in strength that had brought the D-Reaper out in the first place. He had the DigiGnomes transform the Shining Digivolution into Calumon.

With the loss of the power to Digivolve, Zhuaqiaomon, thinking that the Digimon could instead grow stronger by defeating humanity, sent his Devas into the real world. Soon, his servant, Makuramon, discovered Calumon, and attempted to return him Zhuqiaomon, causing the Tamers to follow him in an attempt to rescue him.

After being seperated, and a long, difficult trek across the Digital World, they arrived at Zhuqiaomon's domain. As they battled him, Azulongmon made his appearance. Meanwhile, Ryo Akiyama encountered Ebonwumon and Baihumon in the latter's domain, and soon, they all gathered in Zhuqiaomon's area, just as the D-Reaper was beginning to make its appearance. Here, a compromise was made, and the Sovereigns implored Calumon to release the power so that Digimon could digivolve and fight back. Thus, it was Zhuaqiaomon's plan that prevailed in the end, even though that does not excuse his methods in attacking the Tamers.

The Sovereigns would lead their new army of Mega Digimon to fight the D-Reaper in the Digital World. Later, they would travel to the real world, and help the Tamers by removing the Cable Reaper from the battle.

Notes/Trivia

 * In the dub, Ebonwumon's two heads have different accents; one Irish, one Scottish.
 * Bandai of America confused Ebonwumon and Zhuqiaomon's names, after a slight error on behalf of their Japanese counterpart. The dub for Season 3 managed to correct the oversight, but Bandai still releases their merchandise with the names switched.
 * Baihumon is, physically, the most powerful of all four Sovereigns.
 * Fanglongmon is the only one to have never appeared in any of the media.