"Why don't you help Wyverndale instead?"
King Leonel was left dumbfounded by that question of Edwin for quite a while. He had agreed to help Mihir during the war because Lillian had been persistent enough and had made Leonel believe that that was the right thing to do for the sake of Frostford and also for Edwin.
Leonel had believed that Adeline wouldn't make a capable Queen and he was willing to end the treaty with Wyverndale so that he could get support from the 'stronger and more capable' ruler, namely Reginald.
But now that Edwin was telling him that he was basically going to give a death sentence to his nephew by siding with Mihir, he felt guilty for blindly believing in his sister.