This class seems very cool and flavorful, but unplayable. If you use your main class feature even for one round you fall unconscious for a week. I know that such a strong feature should have a drawback, but... it seems extreme. I don't know enough about balance to make a suggestion, though.
Also, there's no capstone at the moment. Such a flavorful class could have a totally awesome capstone.
EDIT: Right, balance, tier Cipher.