The Raven clearly doesn't want to do any such thing. But if you could provide sufficient evidence that the curse is real and explain who's responsible, perhaps it would be possible to force his hand.
The city needs Falathar. The fact that he's imprisoned in a cell at the palace is surely merely an inconvenience. After all, the heroes of your plays would dispose of this problem easily.
You try not to think about the fact that their problem would involve scaling a six-foot canvas wall on a ladder, unimpeded by guards until it's time for them to make their daring getaway. How hard can it be?