I Am Looking For An Anime Series!?

I am looking for an anime series. I can not remember what it is called
but it is about a young warlock who is in search for the answer to how rescue his sister.
He and his older sister are members of a magic school, they once find this old sword which corrupts his sister.
Along his journey, he is accompanied by two ‘golems’ who are only really interested in treasure…
can someone please tell me what it is?