Gender: Male
First Appearance: The New Olympians series pitch
Other Appearances: Gargoyles original comedy series development
The character of David Xanatos has apparently been bouncing around Greg Weisman's head for some time, for his prototype, Xavier, made it into not one, but two series pitches before being converted to his final form.
In The New Olympians series, Xavier would have basically played the role of Xanatos, trying to ally himself with the New Olympians and thus exploit them. He would have had the same resources as the modern Xanatos.
In the Gargoyles comedy series, Xavier was far different. There, he was descended from the wizard who imprisoned the gargoyles in stone sleep. Further, he had a more petulant, Captain Hook-esque personality. Otherwise, however, he was still Xanatos.
When the dramatic Gargoyles series was developed, Xavier's name was changed to Xanatos, to avoid confusion with the X-Men character Professor Charles Xavier.
Both versions of Xavier were virtually identical to David Xanatos in all abilities and resources. The comedic Xavier was likely less proficient in Xanatos's skills than the New Olympian one was, however.