X.A.N.A.

X.A.N.A. is an evil sentient computer program that was created by Franz Hopper, who was the father of Aelita in the Code Lyoko television series.

Personality
The entity X.A.N.A. has little personality, will, or subconscience. All it cares about is taking over the world and the virtual world of Lyoko.

Appearance
X.A.N.A. has no physical form but it can possess the bodies of humans, animals, and even objects. Its real physical incarnation is believed to be a spectre or shadow of some kind.