Ruby's not like other demons. She saved my life.
In fic, their relationship is usually started during or after Ruby helps Anna in 4.09 I Know What You Did Last Summer and 4.10 Heaven and Hell, though fics do exist that have Ruby knowing Anna from her time as a human.
Owing to Ruby and Anna's lack of popularity with the fandom at large, Annaby is not a very prominent ship in many circles, but has accumulated a loyal fanbase and is one of Supernatural's most popular fem slash pairings.
- Anna & Ruby - A Tumblr devoted to all things Annaby.