Ionia was the Capricorn Saint in the Century XX and another centuries.
History as a hero
Ionia was the Capricorn saint at various times, but, retired from his office. After the war against Hades in the XX century, Ionia will seeAthena's suffering (he hates this, and in the future, will motivate himto become a villain), so, decided help her, although he has been retired; he founded a school of the servants of Athena, but the hard training causes a rebellion, forcing Ionia kill his students. Ionia never forgives himself, and arrested himself in a prison, where months (or years) elapsed. Athena forgives Ionia personally, and ask for him to turn back the Capricorn Saint and turn the principal of Pallaestra. Probably, Athena and the other Saints like Shun and Shiryu, stay hidden, helpless because of them darkness hurts.
When Mars knew about the office of Ionia, propose to him the papacy of new Sanctuary, in exchange, to manipulate Pallaestra students to serve him. Ionia accepts, because he wants the end of Athena pines in the world. He invites Harbinger to become a Saint. He was the most featured Saint of Mars, because his old age and because he always appears as a involved in the story of the other saints, representing Mars.
As Pallaestra principal, Kouga got admiration for him, but, when Kouga invades the Athena's room, discovered that Athena, is not theAthena, who he met... he is Aria, and Ionia uses his darkness Cosmoto brainwash her (to think she is Athena).
The time to capture Pallaestra students has come, and Ionia helps Mars to arrest them in a coffin made by Schiller.
In Capricorn Temple, Ionia fights with Kouga, and his story don't convince him, and, although he rejuvenates, Ionia is defeated by Kouga.