[quote=Sapphire]
Yeah, she has pets/minions to do that for her. Getting involved with mortal lives is not a flaw, becoming obsessed with certain ones is a flaw. As much as I want to believe Eris could have done whatever she wanted, I can't because I believe that Eris must have weaknesses, if it isn't the book of peace then perhaps it is that the goddess of lies and deceit (amongst other things) has to keep her promises.
[/quote]

The Book of Peace seems to only be her 'weakness' because she wills it. She isn't particularly impeded when it's opened, and only uses it as some kind of mcguffin. Something to give the mortals a chance, and for her to take away. I believe it's quite likely that the mark on her chest might be another one of those self-imposed limitations. Also, she's a Goddess. Literally. She might not be omnipotent, but she isn't going to have one definite weakness per se.