Hiver tried to appease you but you fought him without mercy. Unfortunately, he escaped... Having discovered the truth, you and Mir decide to do whatever it takes to fight the Black Wings and stop the Black Mage.
Mir says that he can't just let this go and suggests that you go to the Frog House in Ludibrium Village where you met Hiver in person. Maybe Hiver is still there... Go teach Hiver a lesson.