|Game||Tales of Vesperia|
|Japanese Voice Actor||Megumi Ogata|
Prince Ioder Argyros Heurassein (ヨーデル・アルギロス・ヒュラッセイン Yooderu Arugirosu Hyurassein?) is considered to be the rightful heir to the imperial throne in Zaphias. His primary supporters are the Imperial Knights, and toward the end of the story, he gains the support of the Council.
Ioder is friends with Estelle and Flynn Scifo. Because the Council originally supported Estelle's ascension to the throne, Ragou enlisted the help of Barbos to kidnap Ioder. After the second encounter with Zagi, Yuri Lowell rescues Ioder from his captor's boat as it sinks into the sea. When the party is arrested and sent to Heliord, Ioder repays Yuri by clearing all charges against him. The group encounters Ioder again in Capua Torim, and talks with him about becoming the new emperor. Ioder claims he can not become emperor because the symbol of ascension, Dein Nomos, had been missing for ten years.
Ioder is encountered again in Halure after the residents from Zaphias are evacuated from Alexei Dinoia's takeover. There, he informs Yuri the situation in the capital is growing worse than anyone imagined. Later in the story, he is called to Aurnion, along with the other world leaders, to discuss a resolution to counter the Adephagos threat. Although the party does not realize this, Ioder is encountered very early in the story. When the party first departs from Zaphias and is being given the world map, the voice of the person giving it to the group belongs to Ioder.