Crystal Ball is the seventh son born from a Romalian father, who himself was a seventh son, and an American mother. There are legends that state the seventh son of a seventh son have telepathic powers. Coincidentally, Crystal Ball has shown the ability to read minds, especially when interrogating G.I. Joes. This origin story was told in the Marvel Comics G.I. Joe: A Real American Hero series.
On his file-card for the Hasbro toy line, Crystal Ball was an encyclopedia salesman and was initially called Trance-Master. He obtained his power from a group of evil priests in India who taught him ancient forms of hypnosis and mind-control. He returned to North America where he began to use his powers to take over corporations until he crossed paths with Cobra. Instead of opposing them, he joined their ranks.
No other origin story has been told about Crystal Ball in either the Image/Devil's Due Publishing run of G.I. Joe, or the current IDW Publishing G.I. Joe series.
Crystal Ball was created by Hasbro for the G.I. Joe toy line in 1987. His origin was written by Larry Hama.
Crystal Ball is Cobra's hypnotist. He did not appear in many issues. Perhaps his most prominent appearance was his first. He was a part of a failed attempt by Cobra to kidnap the President of the United States at a baseball game. He manages to hypnotize some Joes, who are running security, so that Cobra can gain entrance to ballpark.
Devil's Due Publishing
In the Devil's Due G.I. Joe series, Crystal Ball goes by the alias of Dr. Scott Stevens and is the therapist to General Philip Rey (who had become the commander of the G.I. Joes when Hawk was severely wounded in battle). He attempts to make General Rey a Cobra agent using post-hypnotic phrases to unlock his mind. Crystal Ball eventually reveals that General Rey is a clone of Serpentor. Duke is able to foil Crystal Ball's plan however, getting General Rey to resist his programming.
In the IDW G.I. Joe story line, Crystal Ball is a high ranking member of Cobra and is often referred to as the "Inquisitor General". When Chuckles destroys an important R&D project (see G.I. Joe: Cobra volume 2), he is sent to question Tomax, Xamot, and Erika Le Tene on the matter.
Major Story Arcs
Crystal Ball was a part of the Hasbro G.I. Joe toy line. The sales of this character were not particularly high, and he was dubbed the "peg warmer" of the toy line.
Crystal Ball also appears in the G.I. Joe novel Divide and Conquer. In this story, Crystal Ball has the power of telepathy and the ability to create illusions.