Responses
As mentioned in the prev chapter Yurirel wanted to kill the Magician. Since he failed to do so, he need someone who has equal amount of mana. Dragons are known to have strong amount of mana. So he bring the dragon prince to the magic circle to activate his dragon form. And since he's the king's lover they will think it as an attack, and will slay the dragon prince.
Wait...what just happened?? Did Yurigel kill the dragon king...???