Ah yes, the "I'm not a villain, I'm just enslaved, and once you free me you'll have my eternal loyalty/love" development.
Which means Kasia's main goal now would be to break him free, because instant balance swing of them losing Ernon AND Tasel's army getting Ernon by way of Kasia.
Not to mention the now magic-capable Kasia being even more of a one girl army herself.