I remember reading a book series during elementary school that had a boy who found a magic stone that went into a belt. I think that he kept finding more of them to keep them from who/whatever the antagonist was. I do remember there being a lot of ravens. They showed up all the time when things were getting tense, and maybe they were an alternate form of the antagonist. I know he was attacked by them at least one time.
It was a series, fairly long, and something you would read around 4th-5th grade. It was written in English. This was somewhere between 15-20 years ago, and I don't think that the books were new at the time I read them.