Would you help me discover the title of this book?

The book is like set in the middle ages or something I believe. I distinctly remember a scene where the main guy had been thrown in prison, and a magical girl whose name was like Elwayin or something starting with an E helped him dig their way out of the prison, and the girl had a magic spell or something that created a magical ball of light that would illuminate areas. I also seem to remember her having a bow with magic arrows that did different things, like create a web or something. Also, there were two big antagonists; a female and a male. I think the male went by the name of the black knight or something, and the female's name started with an A. Also, in the beginning, it describes the main protagonist of working as an apprentice on a farm or something. Thanks!