Prince Solon is the heir to Nexus and the brother of Prince Adrian the traitor. You, as the player, originally befriend him on your ship to the City of Nexus to remove the curse from Ataraxis whereby you are stranded on the Reef of Ruin after the Leviathan destroys your convoy. He will give you quests from the City to go and slay several beasts as well as is the initiator for the quest line in order to charge up Ataraxis' Crystal, in an attempt from raise him from his slumber.
During the final fight with Prince Adrian, he interupts his tranformation to become a Ruin Lord and become a half-mutated monster. After which Adrian sends him flying from the battlefield to fight the, soon to be, Knight of Nexus - the hero.