Rehgar Earthfury was born on Draenor into a clan warring with a band of ogres. He made his first kill long before the normal age of an orc's rite of passage, and was captured by the ogres to be used as a training tool for their youths. However, Reghar grew into a strong warrior, and after slaying many of their young fighters, was sold to the orc arenas in an attempt to recoup their loses.

Despite his young age, he was a superb warrior, and was chosen to participate in the orcs' invasion of Azeroth, leading to his eventual capture and internment. However, unable to subjugate him, the guards sold him as a gladiator to fight for the human, Lord Agrovane. He escaped and became a fighter in underground arenas, gaining riches and fame.
In World of Warcraft: Trading Card Game.

Using his savings, he purchased the Blackrock orc, Bloodeye Redfist, from authorities in Booty Bay, and followed Thrall's teachings, becoming a shaman. After arriving in Durotar, they traveled the fighting circuit, Rehgar teaching Bloodeye the ways of the gladiator. Bloodeye became the Orc's favored champion, dominating in single combat, earning both himself and Rehgar riches. Bloodeye bought his freedom, and the two pooled their money to purchase and train Valeera Sanguinar and Broll Bearmantle to join Bloodeye in team combat.

Shortly after, Bloodeye was killed, poisoned by the mate of a fighter he slew in the arena. Following Bloodeye's funeral pyre, Rehgar set out to find a replacement for his team.

Also not to be confused with Rehgar Earthfurry. That's a whole 'nother bucket of fish.