The "Shitennou" (四天王; meaning "Four Heavenly Kings") were the four loyal and faithfully devoted generals and bodyguards of Prince Endymion. When they were all possessed by Metalia's vast negative energy, they became evil and served Queen Beryl and the Dark Kingdom. The members were Jadeite, Nephrite, Zoisite, and Kunzite. Each of them were named after a different stone.
In the anime, the Shitennou each had distinct personalities and motivations while they served under Queen Beryl. The first of the Shitennou was Jadeite, and his mission was to gather energy from humans in order to awaken the Dark Kingdom's great ruler, Queen Metalia. Jadeite was a master of disguise and enacted various schemes to obtain energy. He posed as a radio host, a gym trainer, a talent show promoter, a cop at a carnival, a shrine worker, and a sea captain, all as part of various energy schemes. While he was often unsuccessful, it was stated by Queen Beryl that he had gathered a significant amount of energy for the Dark Kingdom. In episode 13, Queen Beryl commanded Jadeite to defeat the Sailor Guardians, and when he failed to do so, he was sentenced to eternal sleep. Jadeite had never been shown to interact with the other three Shitennou, but it is implied by later comments that they were at least familiar with him.
After Jadeite's demise, Nephrite was chosen by Queen Beryl to serve as the next strategic commander. In contrast to Jadeite's energy gathering schemes, Nephrite's plans focused on collecting large amounts of energy from a single target at the peak of their energy. The stars are what provided Nephrite with each of his targets. While infiltrating the human world, Nephrite took on the persona of Masato Sanjoin, a successful entrepreneur. Masato Sanjoin/Nephrite was noted numerous times to be exceptionally handsome, so much so that he became the love interest of Usagi's good friend Naru Osaka. While he initially used Naru in an attempt to obtain the Silver Crystal, Nephrite eventually started to develop feelings for her. His confusion over why Naru kept appearing in his thoughts finally culminated with him saving Naru from three Youma. He and Naru retreated to the park, where he promised Naru that someday he would try a chocolate parfait with her. He was unable to keep his promise, however, when the three Youma he had previously spared ambushed him. Nephrite sacrificed himself to save Naru from their assault, and to her despair he died beside her, telling her that he was glad to have met her.
From as early as his initial appearance, Nephrite had an ongoing rivalry with Dark Kingdom commander Zoisite. Zoisite first appeared on episode 14, along with Nephrite, and insisted that Nephrite's downfall would be his own overconfidence. Nephrite simply dismissed his cohort, and Zoisite did not appear again for several episodes. However, animosity between the two later built up, as a result of Zoisite's numerous provocations and Nephrite's resulting hostility. After Nephrite appears before Queen Beryl to steal Zoisite's job in searching for the Silver Crystal, Zoisite is shown being comforted by his lover Kunzite, and the duo later plot against Nephrite to prevent him from being the one to obtain the legendary crystal. It is Zoisite who orchestrates Nephrite's demise, by sending the Youma who defeats him via a surprise attack.
Beginning in episode 25 after Nephrite's death, Zoisite is tasked by Queen Beryl in obtaining the seven Rainbow Crystals, of which the original Silver Crystal had been divided into by Queen Serenity. He is able to obtain the majority of the crystals but loses some to both the Sailor Senshi and Tuxedo Mask. Throughout his arc, Zoisite is often accompanied by his partner Kunzite, who encourages him and is ultimately the sole source of Zoisite's determination and persistence. In episode 33, Zoisite states in an internal monologue that he is only doing things for Kunzite and that he would even die for his beloved. Later in this episode, Zoisite dresses up as Sailor Moon in order to get the final Rainbow Crystals in Tuxedo Mask's possession. The plan which he and Kunzite coordinated is spoiled in the end by the appearance of Sailor Venus, however, Zoisite is still able to reveal Tuxedo Mask's identity. Upon recognition of the unmasked Mamoru Chiba as the former Prince Endymion, Queen Beryl orders Zoisite and Kunzite to bring back Tuxedo Mask alive. After tricking Mamoru into giving up his Rainbow Crystals, Zoisite lets his contempt get the best of him, and he attempts to murder Mamoru despite Beryl's orders. When he ends up impaling Tuxedo Mask with a crystal, it catalyzes the Moon Princess's awakening, and she delivers a critical blow to Zoisite from the Moon Stick. Kunzite appears then and helps Zoisite to his feet, but a furious Queen Beryl shoots a powerful attack at Zoisite, bringing him to near-death. In his final moments, Kunzite holds Zoisite in his arms and grants him his final wish of a beautiful death.
Kunzite takes over after Zoisite's death, but he is often antagonized by the brainwashed Prince Endymion. Before his departure, Zoisite informed Kunzite that the Moon Princess was Sailor Moon, so Kunzite's schemes focus on determining the identity of Sailor Moon, as well as obtaining the Silver Crystal from her. He is never able to succeed in these plots, due in part to meddling by Prince Endymion, who occasionally turns back into Tuxedo Mask to defend Sailor Moon despite his brainwashing. Kunzite eventually is killed by Sailor Moon, when she reflects his dark energy boomerangs using the Silver Crystal. Kunzite uses his dying words to call out to Zoisite and asks for him to guide him to the world where his soul is.
In the anime, there were no references to the Shitennou's past lives as servants of Prince Endymion whatsoever; nor was they any slightest indication that they had any romantic relationships with Sailors Mercury, Mars, Jupiter, or Venus. They were often rivals and were discarded once they were no longer useful or severed their purposes.
Queen Beryl had ruthlessly murdered both Zoisite and Jadeite, while Nephrite had brutally died at the hands of Zoisite's Youma, and Kunzite had perished when his attack was deflected back at him by Sailor Moon's supremely strong Moon Healing Escalation attack combined with the almighty Silver Crystal's own abilities. While they weren't directly seen or heard from again in future seasons, there were two cameos in Sailor Moon R featuring the Shitennou. The first was of Jadeite, in which someone appeared dressed like him in a Sailor Moon play during the Makai Tree arc. The second cameo was of Zoisite in episode 70, where he appeared as a chibi when Koan hit Yuuichirou in the head with a bag.
They were originally the guardians of Prince Endymion, like the Inner Senshi to Princess Serenity. Suspicious of The Moon and its constant surveillance of Earth, they often argued with their prince about it. Their suspicion led them to turn on the prince and turn to Beryl. Despite this, they still cared for their prince and were shocked by his death. They are still rivals but also care for each other and are shocked by each other's deaths. When the Silver Crystal appeared, it returned the dead Jadeite, Nephrite, and Zoisite to life and returned Kunzite's memories of the past. They then dissolved into stones bearing their name, as did Kunzite when he is later killed. They later speak to Mamoru through the stones, telling him how Metaria could be killed and to be happy. Mamoru kept these stones and called on their spirits for advice and guidance throughout the manga, most especially during the Dream Arc, when he came into his powers as the holder of the Golden Crystal, the Earth's Sailor Crystal.
Romances with the Inner Sailor Guardians
Naoko claims she was thinking of the past lives of these characters, which implies a possible love affair between the four inner Sailor Senshi and Shitennou in the past. However, only Kunzite's relationship with Sailor Venus and Jadeite's with Sailor Mars have canonical support.
The live-action series combined elements from the anime and manga: the Shitennou were still Mamoru's guardians, and were also evil and vying for Queen Beryl's attention. They could also come back after being killed, unlike in the other two continuities, so the relationships lasted longer and were more complicated. They were also closer to being human, with Nephrite being turned into one and Kunzite being turned from one. Their personalities were developed and their memories of the past life were much closer to the surface, which resulted in more tension with Mamoru. This was especially apparent with Kunzite, who blamed his master for what happened to the planet Earth. Their character designs were also completely redone. In the Special Act, the Shitennou work with Mamoru so they can defeat Queen Mio. They all later watch Usagi Tsukino and Mamoru's wedding.
The Shitennou appeared in several of the musicals, with slightly different roles in each. In "Pretty Soldier Sailor Moon ~ An Alternate Legend - Dark Kingdom Revival Story", the Shitennou were romantically paired with the Inner Senshi, making the musicals the only version of the series in which those relationships were canon. In "Pretty Soldier Sailor Moon ~ Starlights - Legend of the Shooting Stars", they appeared again disguised as the "Jewel Metalias".
The musical "Pretty Soldier Sailor Moon ~ The Advent of Princess Kakyuu - The Second Stage Final" introduced a group that called itself the "Neo Shitennou" or the "New Four Heavenly Kings" and included three members who were not in the original group. The members of the Neo Shitennou were Kunzite, Hematite, Hiddenite, and Kalunite. No explanation was given for why they had different names, although Hematite, Hiddenite, and Kalunite strongly resembled Zoisite, Nephrite, and Jadeite respectively. They worked with the reborn Queen Beryl under Sailor Galaxia, though the five of them were simultaneously plotting ways to get out from under the powerful Sailor Senshi's rule. As part of their plans, they had civilian guises as the "Jewel Managers".
In Pretty Guardian Sailor Moon - La Reconquista, the Shitennou disguise themselves as a boy band known as Pandemic 4.
In Sailor Moon Crystal, the Heavenly Kings are much more like their manga counterparts. Unlike the 90's anime, they are not rivals and cooperate more like teammates. Queen Beryl did not try to destroy them for failure or threaten them for doing so, and they survive for much longer unlike in the manga. Like the manga, they were the most loyal and devoted servants of Prince Endymion during the age of Silver Millennium, and they recovered these memories in Episode 10; only for Queen Beryl to brainwash them again. In the same episode, they are revealed to be the former lovers of the four inner Sailor Soldiers when they had followed their Princess to Earth.
They were finally fully released from Queen Metalia's control when the senshi combined their own Sailor powers to perform Sailor Planet Attack. Before they could have a proper heartfelt reunion, however, Queen Metalia intervened and obliterated their physical selves entirely. Distraught and heartbroken, their voices reminded the Sailor Senshi about their true mission and not to cry.
Although their physical bodies have perished, their strong spirits/souls still exist within their respective colored stones to give advice, guidance, and wisdom to their one true master. In the 12th episode, their stones had protected their master from being stabbed to death by the sacred, Sword of the Silver Crystal to return Prince Endymion to life once again. The spirit of Kunzite later appeared and gave Endymion vital information on how to eliminate Queen Metalia once and for all. The other three then appeared and assured Mamoru that they would always stay by his side and knew that he and his Princess would live happily ever.
In Episode 18, Mamoru had used his newfound mystical abilities to call upon his four subordinates. Kunzite had said that he detected very strong evil energy coming from the Black Crystal earring and that he, Endymion, needed to believe strongly enough in his own abilities if he wanted to protect the person most dear to him. Despite appearing in the Dream Arc of the manga, the Heavenly Kings don't appear and aren't even mentioned in Sailor Moon Eternal.
- Interestingly, in the anime, three of the four Shittenou have appeared as cameos or been referenced after their deaths; Jadeite's likeness appeared as a character in an (in-universe) live-action Sailor Moon performance in episode 58; Professor Tomoe quoted Nephrite's phrase in episode 119 when he used the phrase Nephrite used to find his victims in various episodes, ("'The stars see all, the stars know all...' was something someone once said."); finally, Zoisite appeared in a very brief cameo after Koan bumped into Yuuichiro during episode 70.
- In the 90s anime, two of the four Shitennou discovered Sailor Moon's civilian identity shortly before their deaths:
- Jadeite discovered the identities of Sailor Moon, Sailor Mercury, and Sailor Mars in episode 13, the same episode in which he died.
- Nephrite discovered the identity of Sailor Moon in episode 24, the same episode in which he died.
- Zoisite discovered that Tuxedo Mask was Mamoru Chiba in episode 33, and that Sailor Moon was the Moon Princess in episode 34, before dying in episode 35.
- In the 90's anime, of the four Sailor Senshi and Shitennou pairings, only Sailor Jupiter and Nephrite never meet each other in the present (as he died in the episode immediate prior to her first appearance). In the manga, however, she was the one who killed him. Jadeite and Nephrite were the only ones killed directly by the Sailor Senshi paired to them by one of Naoko Takeuchi's sketches in the manga, while Zoisite was killed by Sailor Venus and Kunzite by the Sailor Planet Attack. In the anime, Sailor Moon killed Kunzite, Queen Beryl killed Zoisite and Jadeite, and Zoisite's Youma killed Nephrite.
- Zoisite was featured in the manga side-story, Casablanca Memory.
- During the 90s anime, Kunzite was the only one of the Shitennou to never use a disguise; Jadeite used numerous disguises, Nephrite played the extended role of Masato Sanjoin as well as dressed as Tuxedo Mask once, and Zoisite dressed up as Sailor Moon.
- In the 90's anime, Jadeite was the only one in the group to not introduce himself as a member of the Shitennou. He never once used this term, and Nephrite was the first to introduce himself as one of the Shitennou. Zoisite and Kunzite also followed Nephrite in referring to themselves as a part of the Shitennou of the Dark Kingdom.
- While 四天王 directly translates to "Four Heavenly Kings," this term can also be translated to mean something along the lines of the "Great Four" or the "Big Four".