The Shadow Princess

"Once upon a time there was a Shadow Princess. Everyone in the Kingdom called her like that, for a dark, gray aura enveloped her wherever she was."
Laila was born cursed and her parents no longer know who to turn to in order to cure her. So they promise the hand of the young princess to the knight who can find a solution.
Here is a fairytale like the others.
But...
As candidates of all kinds try one after another to save the princess, the commoner Priya - daughter of the woman responsible for the curse - is given the same mission that so many others have failed.