In the "Future Tense" dream universe created by Puck, the Xanatos Program was a limited artificial intelligence, created by Lexington as a facade through which he could control Manhattan, and eventually the world. It had all of Xanatos's memories and personality, but it lacked all of his redeeming characteristics.
The Program destroyed Alexander Fox, who challenged it in its virtual domain, and later slew Brooklyn, Angela, and Demona, before it was eventually destroyed by Goliath. However, copies of it were sent across the World Wide Net, where they would take over the world's computer systems.
In cyberspace, the Xanatos Program was like a god. Visually, it manifested itself as Xanatos, clad in a bulky version of his Steel Clan armor, and employing similar weaponry. "Xanatos" could warp the fabric of his virtual world to his will, changing himself, others, and the environment around him. His only notable weakness was that his power was not absolute- another being of sufficient will could counter his control.