|Game||Tales of Phantasia: Narikiri Dungeon (X)|
|Japanese Voice Actor|| •Motoko Kumai|
|Character Designer||Daigo Okumura|
Dio fell from the sky prior to the story's opening along with his twin sister, Mel. The two of them were found by a mysterious stranger who raised them in the Narikiri House until they were around thirteen. Up until that point, nobody knew quite where they came from, but one day, a woman named Norn appeared who seemed to know about their past. Apparently, they would once committed terrible crimes and their punishment was a curse from the gods. The only way to stop this would be to travel to the past and undo what they did, but first they had to meet the Heroes of Eternity and fight off twelve Summon Spirits in the Ordeal of Spirits (せいれいのしれん Seirei no Shiren?).
Eventually, Dio learned that he was a 27-year-old soldier on Derris Kharlan named Dios Bandi in a past life. Together with his sister Meltia, he used to build incredible magitech weapons for his home country. When his father, the general of his country, died, he was ordered to fire the Magitech weapon, a bullet of hatred. Doing so doomed Derris Kharlan, draining all of the mana and killing their World Tree. Dios then died, embittered and cynical.
Dio and Mel proceed to fight their past counterparts at the end of their Ordeal to absolve themselves of their past sins. When Dios and Meltia are killed, they say how the protagonists have broken the chain of fate by killing their past selves, their present selves cease to exist. On that last dark note, Dios merges with Dio. Norn saves them, only to test them herself. When she is defeated, Dio ceases to exist, but he is reborn without memories and given to the player once more.
- Dio is ambidextrous, using swords and paintbrushes with his left hand, while using daggers and ninja blades with his right.
- In Tales of Berseria, a set of Dio and Mell's outfits can be obtained as treasures stored on the Van Eltia. Diomel Island, where the treasure is obtained, is also a reference to Dio and Mell.