Karina is a homunculus with a split personality. She is both Doubt and Vanity, but can switch off on one side depending on her mood. When she is stable as one person, she is Karina. When she is Doubt, she is more shy and modest, unsure about a lot. Her ouroborus is on her left shoulder. But when she is Vanity, she is extremely egotistical and straightforward, and more than happy to start a fight. Her ouroborus is on her right shoulder. When stable, both ouroborus are visible. Karina lost most of her memory, but she knows who and what she is. She has a connection to Envy, and was in fact his partner before she was kidnapped and her memory was wiped. She doesn't realize this, but Envy will continuously try to make her remember and cooperate. Every now and then, she will have painful flashbacks that render her helpless for several minutes, or will even knock her unconscious.
She is just a bit shorter than Envy. Her hair goes past her calves, and it is a silvery-grey color. Her eyes are bright green, and her skin is just between tan and pale.
Both personalities like Envy immensely, but try to hide it as much as possible. This becomes harder when the personalities are stable and she is one, Karina.

In this image, light Karina is Doubt, and dark Karina is Vanity. No ouroborus was drawn at the time because I was unsure of where to put it.