Questions about hierarchy in Zed's Order of Shadows and shadow magic in general

I know there are 3 ranks in the order and they all teach eachother with kayn being above them and zed being above kayn. I would just like to know what they are called. Also, is there a difference between learning shadow magic (like how kayn learned from zed) and acquiring the knowledge (zed and the mysterious box)? Does the strength of the user also scale with how powerful/how much they can control the shadow magic? are there other artifacts that hold knowledge of shadow magic or was that box the only one therefor confirming Zed is the only one who has ALL the knowledge of it?