He was once known as Terrence "Smitty" Smith, another former paleontologist. Terrence Smith, Anton Mercer, and Tommy Oliver went on an archeological dig together. Smitty and Tommy applied for the same position in Mercer Industries, and Tommy got the position. Smitty got a job with a different company. Smitty was conducting an experiment, when a horrible accident happened. Smitty laid on the floor until [Mesogog] reached down and offered his hand. Smitty grasped the offered hand. Smitty had been presumed missing. Mesogog rebuilt Smitty transforming him into Zeltrax. From that point on, Zeltrax has plotted revenge against Dr. Oliver for what had happened to him.
While serving Mesogog, he had a romantic interest in his partner, the mutant warrior Elsa. Unfortunately, she didn't feel the same way about him, at all. Elsa would often disrespect him and boss him around.
Mesogog put him in command of the Tyrannodrones. Once the Dino Gems were removed, Zeltrax was sent to retrieve those who had taken them. Zeltrax had followed Kira Ford, the holder of the Yellow Dino Gem, through an invisiportal to the other holders of the Dino Gems (Conner McKnight and Ethan James) and their teacher, Dr. Tommy Oliver. Zeltrax fought Dr. Oliver, and was told by the human to inform Mesogog that Dr. Oliver was back.
Zeltrax had later returned with greater force. He used the Aerial Assault Vehicle to attack Reefside, but it was destroyed by the Dino Thunder Rangers' Thundersaurus Megazord. Zeltrax was sent to capture Dr. Oliver when he was at Hayley's Cyberspace. Zeltrax admitted to Oliver that he had a powerful hatred for him. As Elsa and Mesogog would return to Reefside and be in disguise in their human personas, Zeltrax would be left by himself at the fortress to monitor the activity.
Zeltrax wanted to make himself stronger using the Geno Randomizer. However, when he did that, nothing happened, except he managed to clone himself a powerful, youthful version of himself called Golden Rod. Golden Rod was supposedly his son, and Zeltrax used him to help him destroy Dr. Oliver. When Golden Rod was destroyed, Zeltrax vowed a large amount of vengeance on Dr. Tommy Oliver. Zeltrax had used the aid of the Triptoids to fight the Rangers. Zeltrax fought Anton Mercer's son, Trent Fernandez, to stay at his position as Mesogog's second in command. Zeltrax later built the Surface Assault Vehicle for the Rangers to fight.
Zeltrax was assumed to have been destroyed by Tommy, but had later returned to steal serum from the Tree of Life to make him stronger. Zeltrax returned in a much stronger form, now having a new mission to destroy both Dr. Oliver and Mesogog for betraying him. Days later, Zeltrax had returned and built the Zel Zord and captured Elsa, who was now free from Mesogog's hold over her, and used her as leverage over the Rangers, after he had destroyed the DT Lab. Zeltrax fought the Rangers in his Zel Zord, and was later destroyed by the Dino Thunder Rangers.