Idumeans also known as Red Jews are the descendants of Edomites forcibly converted to Judaism by John Hyrcanus around 100BC when he ordered the entire population to be enslaved and then freed. Hence they are also known as Ercolians or Hyrcanian Jews. Although they accept the Mishna they do not have a very sophisticated understanding of Judaism and are comparable to Samaritans, Falashahs and Karaites. They worked hard to make Hagarim and Toshavim out of all the gentiles of the Middle East such as for example the Elagabalites.
The Idumeans made a treaty with Yazdegard III in 636. Yazdegard accepted their religion and they accepted him as their king.