Lust is a Homunculus and one of the first antagonists in the Fullmetal Alchemist series. She is usually partnered with Gluttony to whom she appears to have a particular, almost motherly closeness. Her Ouroboros mark is located on her collarbone, just above her large breasts.
(Info grabbed from here http://fma.wikia.com/wiki/Lust)
// I would've used the green alice dress but it just didn't look good. It was way too green