"You can enslave this land and this body, but you can't rule my spirit! The Prince and the Princess will wipe out you and your minions." - Elios to Nephelenia, Act 36
Elios is the priest of Elysion, the holy land that protects Earth from within. Elysion is a beautiful garden that lies at the heart of the Earth. Elios' mission is to protect the Earth and its Prince; he is, in a way, Mamoru's guardian spirit.
Elios is a young man with serious brown eyes and white hair; he actually has two forms. In his pegasus form, he is a white horse with sweeping white wings and a golden horn. In his human form, it seems that he can keep the horn or leave it. He is dressed in a flowing white wrap-robe with blue trim; his forehead is marked with an oval.
As a priest, his only power is to pray for salvation and assistance. However, his powers should not be underestimated. He did not have enough power to banish evil completely, but his powers were sufficient to hold it at bay. Elios also possesses indomitable resolve; although he suffered a lot of pain, he managed to hold on and fight Nephelenia throughout.
He first appeared to Usagi, Chibiusa, and Mamoru in Volume 12, when the darkness of the eclipse gave Nephelenia the opening to attack. Chibiusa heard a bell ringing, and turned. A winged horse stood in a grove, pure white against leafy green. He stared straight at the girls, whispered, "Help me... maiden..." and disappeared.
When Nephelenia made her bid for power, her method was to attack from within. She herself was the evil in the heart of the Moon, eating away at the power of the Silver Crystal. However, the Earth was protected by Elysion. She set a curse on Elysion, contaminating it with darkness and nightmares. Elios did his best to keep it from spreading, but she captured him instead. When he refused her, she placed his Pegasus-body in a cage.
However, Elios was able to escape the curse for brief periods of time, and send the image of his spirit winging over the world. He advised Usagi and Mamoru, and informed them that the sickness inside Mamoru (he'd been having pains and coughing up blood) was in fact a reflection of the curse on Elysion.
Mamoru represented the Earth in more ways than one; it seemed that his physical health was tied to the Earth's. The curse devastated the beauty of Elysion, and therefore ravaged Mamoru's body as well. (It was also tied to Elios; as the Pegasus, he complained that he couldn't breathe.) Only when the senshi killed Nephelenia and freed Elios did Elysion return to health.
There's an interesting duality about Elios-as-human and Elios-as-Pegasus; he seems to be able to become either at will. When his spirit was in human form and Nephelenia hurt his Pegasus body, his human image sprouted wings while he spasmed in pain; when the pain subsided, the wings disappeared. At the end, when he was free, he called up the Pegasus, and leapt on its back in human form. So apparently he can become both at once, however paradoxical that may seem.
Elios is destined to be with Chibiusa, when she grows up and becomes Princess Lady Serenity. He therefore made a special connection with Chibiusa as a child. He came to her bedroom window one night in Pegasus form and bade her ride on his back. Then he sprang into the air, taking her for a wild, glorious flight over Juuban, and gave her a little bell. "When you need me," he told her, "call me with that bell."
When Usagi and Chibiusa were attacked by lemures, Chibiusa rang the bell; Elios appeared and gave them new weapons, the kaleidoscope Moon Rods. Sailormoon promptly destroyed the enemies. After the battle, Chibiusa became really insecure, thinking that she'd never be Sailormoon's equal, and that she'd never grow up. Elios appeared to her, kissed her gently, reassured her, and disappeared. At that point, Chibiusa fell in love with him, and Elios replaced Mamoru in her affections.
In Greek mythology, the Elysian fields were the land of the blessed. The place was delightful, with "soft green meadows, lovely groves, a delicious life-giving air... an abode of peace and blessedness. Here dwelt the great and good dead, heroes, poets, priests, and all who had made men remember them by helping others."
- Edith Hamilton's Mythology
As with all of Naoko's names, the English spelling of the name is up to you. The kana for "Elios" is "E - ri - o - su." Others have translated the name as "Helios," which is also fine. Same goes for "Elysion," whose kana are given as "E - ryu - shi - o - n" - giving it the name of the paradise of Greek mythology supports Elios' statement that Elysion is the holy land of the Earth. According to the knowledgeable Ian Miller, "Helius is the Latin spelling of the Greek Elios. That's it. The same goes for Elysion (Greek) and Elysium (Latin). Most people use the Latin forms of the names."
For a closer look at Elios...