The Rune Warriors, often referred to as Rune slaves or rune servants, were a creating of the Circle]] mages. They were mighty warriors or mages who were bound to Rune stones by the power of the Allfire. These Runestones allow a summoner, who had to be the owner of the rune, to command the Rune warrior.
More importantly, the owner of the Rune could summon the respective warrior or mage completely, meaning he would summon him in a real, living body. That way, the Rune warrior would hold onto all of his skills and memories which he had acquired before and after he got bound to the rune. That allowed the Circle mages to have strong and loyal servants.
The Rune power faded after the end of the Circle, and with her the monuments. The Rune warriors that were trapped without a body in their runes during that time died and were released from their servitude. Those that owned a body during the complete annihilation of the power survived and could live their lives until their death.