Adria is a character that has been in the “Diablo universe” for as long as Deckard Cain. Parts of her story have been scattered through Diablo III, in the form of journals that players can pick up as they go through Story Mode (or by doing Bounties). Those journals leave a lot out, though. More of her story can be found in the Book of Tyrael.
In this blog, I will put all the pieces together, in chronological order, as best I can. The thing to keep in mind about Adria is she has spent her life seeking power. Her desire for power is the motivating factor behind everything she does.