Once upon a time in medieval Europe there were two major families who ruled bordering provinces. They lived peacefully together for sometime until an evil tyrant from another realm invaded with an army that neither family could contest but only appease.
The evil tyrant with no contest from either family made both families subject to his rule. During the invasion, the tyrant’s overpopulated subjects began to settle among both provinces. Both families were unsettled and could not support the growing population of the tyrant’s subjects. The tyrant decided to be merciful and hold a tournament pitting both families against each other. The victor would become the family to rule a combined province.
Rules must be adhered in this tournament by the families or else they will lose control of their province and subject to exile. At the start only common fighters of each families are called upon to fight in the name of their house. When a fighter reaches the other end of the battlefield, the family of that fighter may call upon a champion to fight (becoming a king).