Elsa is a servant of Mesogog and originally believed in her dream to see the world reverted to a primordial state under the control of the dinosaurs.
She loves to insult and torment friend and foe alike, including her ally Zeltrax, and seemed to be romantically interested in Tommy Oliver.
For most of the series, she pretended to be Principal Randall, the head of Reefside High School where the Dino Thunder Power Rangers go to school.
In the episode, "House of Cards", after Elsa confiscated a card of the powerful Ruby Dragon monster from the card-game "Dragon Wars" from Ethan James (Blue Ranger), Tommy entered her office on Ethan's behalf in an attempt to speak to her about getting it back, and in the process inadvertently exposed her as the evil Elsa, and to the entire class while she was fighting him outside of the high school. Before retreating, Elsa has the Rangers tell the school board that Principal Randall has resigned.
Over time she grew to distrust Mesogog and plotted to expose him when he was the most vulnerable. She feared that he would eventually tire of her and her failures and destroy her. She even created a potion that separated Mesogog from Dr. Anton Mercer.
Mesogog decided to sacrifice the evil powers which he had granted to Elsa in order to help power his trans-mutation cannon. With that, she was reverted to a normal human form, with no memory of who she was as Elsa by the life-force extractor. The loss of her powers also meant she was good again. At the end of the series, she attended the high school prom and danced with Dr. Mercer.
Elsa was played by Miriama Smith
Read more about this topic: Villains In Power Rangers Dino Thunder