The Accords of Vo Mimbre were an agreement between Arendia, Tolnedra and Aloria that helped to set the course for the history of the West after the defeat of Torak.
After the Battle of Vo Mimbre the barons of Vo Mandor and Wildantor attempted to offer the crown of Arendia to Brand. He refused, but proposed joint rule between Korodullin I and Mayaserana I. They flatly refused - at first. Polgara has them confined together at the top of a tower in Vo Mimbre. Alone.
Later, the monarchs of the West gathered at Vo Mimbre have some serious discussions, ultimately ending with the Accords of Vo Mimbre. Its terms include the establishment of the Rivan King as Overlord of the West, and that he'll have an Imperial Princess of Tolnedra as his wife. The princess must travel to the Isle of Winds and present herself to the throne on her sixteenth birthday.
It is in defiance of this treaty that Ce'Nedra runs away from home, starting her journey.
"It's an old treaty," [Ce'Nedra] said. "I didn't sign it, so I don't see why I should be bound by it. I'm supposed to present myself in the throne room at Riva on my sixteenth birthday." -Queen of Sorcery