Complex sentence: The king and the nobles'faction agreed to a solution advanced by Agnes of Courtenay, who, herself disgruntled with Guy's behavior, was willing to reach an accord with her one-time rivals.
Split into simpler sentences: The king and the factional leaders agreed to a solution advanced by Agnes of Courtenay. Agnes, herself disgruntled with Guy's behavior, was willing to reach an accord with her one-time rivals.