Wikipedia
Octar or Ouptaros was a Hunnic ruler. He ruled along brother Rugila according to Jordanes in Getica, "...Mundzucus, whose brothers were Octar and Ruas, who were supposed to have been kings before Attila, although not altogether of the same [territories] as he". Their brother Mundzuk was father of Attila, but he was not a supreme ruler of the Huns. According to Priscus their fourth brother Oebarsius was still alive in 448 AD. Their ancestors and relation with previous rulers Uldin and Charaton are unknown.
Similar dual kingship, possibly a geographical division where Rugila ruled over Eastern Huns while Octar over Western Huns, had Attila and Bleda.
Octar, identified with Ouptaros, according to Socrates of Constantinople died in 430 near Rhine, "For the king of the Huns, Uptaros by name, having burst asunder in the night from surfeit, the Burgundians attacked that [the Huns of Uptaros] people then without a leader; and although few in numbers and their opponents many, they obtained victory".