He is different than most kings, he is knowledgeable, but his refusal to accept things often gets in the way of his knowledge...
Allow me to anolyze your character Yes Man.
Cassamir is smart, clever, but arrogant. He can't stand it when things don't go his way. So much so that he often makes blunders that cost him allies.
When he is angry, he tends to not think ahead, and at this point, he is desperate to please Boethia, who he has sort of pissed off...
Aventius is your typical overzealous monarch, which is a good character for this RP.
He is the antithesis of Flavius, a man who doesn't want his position, but will cling to it no matter what, 'cus if he dies, everything falls apart. Aventius has a strong belief, and thinks he can change the world. A dangerous belief.