Lust wants the Philosopher's Stone so that she can become a human. She doesn't want to spend her entire life as the product of a failed human transmutation, so she seeks out the stone to quench her desire. She, and the rest of the Homunculi, except for Wrath and Greed, cannot perform alchemy themselves, which is why they have to get other people to do it for them. Along the way, Lust has manipulated many people, including Father Cornello, Mugear, Shou Tucker, and Lujon. She kills most of the people she manipulates as soon as they are no longer useful to her. Lust also has a secret desire for Scar. He seems to care about her romantically as well, because we catch him staring at her and thinking about her intently in episode 40. It also makes sense that he would love her because in a flashback we see Scar's brother, as he is about to die, whisper to Scar (and referring to his dead love that he tried to resurrect): "Be honest. You liked her too, didn't you?" Scar's eyes went wide. Because Lust is the Homunculus of that same woman, it's completely obvious that he would be in love with her! In episode 42, Scar jumps in front of bullets to keep them from hitting Lust, even though the bullets wouldn't have harmed her. (He claimed that his body moved out of reflex.) He soon after uses the last of his strength to activate the huge transmuation circle he had drawn around Liore. (That was what turned Al into the Philosopher's Stone.) Shortly after, Scar dies. Lust takes his head into her arms and whispers "You loved me?". It's my favorite scene in the whole series! Scar/Lust is my OTP in FMA. I just love them so much! They even show up at the end of the movie together, which is my favorite scene from the movie!
