Ænigma is a tall white Jackalope with no face and long claws.
Death Note Movie OST - "A Heart Attack" for most cases
Ænigma has little biology to speak of, X-rays of her sometimes show her as she is normally seen (clothes included) and sometimes show nothing at all, her blood is blue and has the mass of a helium balloon. She has some sort of sight and smell but it is unclear how it works. Blind people can see her, deaf people can hear her footsteps and insane people can't seem to notice her. Overall Ænigma is a Scientist nightmare, but she'd most peoples nightmare anyways.
Ænigma is either a psychopathic stalker or a lonely child at heart. Either way she never speaks (though this might be due to her lack of a mouth). She shows a natural curiosity towards mobians and humans who interest her. If her "friends" are harmed she might mercilessly kill the attacker.
Ænigma is said to have been created by gods in answer to a riddle with no answer. The gods were tricked into creating an answer to this riddle, believing there was really an answer. The being created was Ænigma, who was not really alive or dead or even real.
Just by being around Ænigma causes the air around her to become thin and video feeds with her in it to distort. She can also can teleport as long as she is not being looked at and her destination is not being watched either. She can move extremely fast when watched by only one person and her strength seems to be as strong as needed for any situation. A single drop of her blood can give someone a psychic link to her if they have something in common with her. Finally she can stretch her arms and fingers to any length.
She becomes unstable around open books(though this sometimes makes her more dangerous). She also moves slower the more people there are watching her.