Dr. Spector

Dr. Spector is a friend of the Avatar on Earth, and as the name says, an academic. He also is an adventurer.

Spector was thrown to Eodon some time before the Avatar, with his assistant Fritz, and went insane after an encounter in the ancient city of Kotl, starting to have world conquering plans. His plan included putting the usurper Huitlapacti on the throne of the Nahuatla Tribe, by granting him invulnerability. In Savage Empire, the Avatar had to restore Spector's mind by shutting down the control panel in Kotl, before he would help on the quest (prior to this, the Doctor was actually a threat). In the end, he returned to Earth together with the Avatar.

Spector also stood at the Avatar's side in Martian Dreams, after they both received a mysterious package that showed a photo of both of them in the past. He was very helpful in the quest on Mars 100 years in the past, being the brains of the party. He returned to the present with the Avatar in the end, after their mission was done.

Trivia

 * This is, of course, Warren Spector's alter ego.