Reason

Now, why is Duke Myghell supporting me, when he actively hates my gut to the point that he poisoned me? Well, the answer is simple. Even though he hates me, the love for his daughter triumphs over that hatred. And when his daughter asked him to back me in this argument, even though he had doubts as to what was going on in her mind, he decided to do it even without hearing what she had to say. That is the sort of bond that Myghell shares with his daughter.

I mean, did I expect him to come around this easily? Obviously not. I mean, even though I knew that Duke Myghell really loved Elanor, I didn't expect him to just succumb to her words. But then again, I remember what Karius said. The Duke did anything and everything to ensure that his daughter was happy and more importantly safe.