The mistress smiles, as she sees that Ruby is quite capable of reading, and, once she finishes with the first, small book, she hands the elf a somewhat thicker, and more complex tome, this one on the nature and kinds of demons that are commonly found in the Abyss. A DC 15 Wisdom check allows Ruby to memorize enough of the book, that it grants her a +1 bonus for identifying and Cha checks against demons, as well as allowing her to treat Know: Planes checks as trained for demons, even if she doesn't have any ranks.