I can only find mention of the Autherial Equipment in the Wikia. They are very broken and contain no specifics about the abilities. Does anyone know, for instance how the circlet works, if it absorbs the power of the last stone you used or if when you take it off, it disperses? Other questions like what type of armor is the shield? Heavy or Light? And what is needed to craft them, seeing as how I haven't started the quest but would like to go in prepared. Anything you know would be appreciated.

Dont worry about what you need to make them, its provided for.
circlet works fairly simply - choose a stone, then choose another stone, now you have both those abilities! If you want to change it then change stones.