Mercer was a  brilliant and rich scientist who worked with Dr. Oliver on the experimentation of dinosaur DNA. During their work together Mercer did secret Dinosuar DNA experiments on himself. Therse experiments transformed him into the evil Mesogog. Mesogog was determined to bring the world back into its prehistoric glory. Mercer did not agree with his alter ego and did everything he could to stop him.  Mesagog took Oliver's work and used it to create his evil army. Years  later Mesogog resurfaced. He seeks the Dino gems to help create a prehistoric utopia. He will stop at nothing to get the gems from the Power Rangers. But the Dino Thunder Rangers have provided a constant menace to him and his plans. Mercer also resurfaced in his human form after Dr. Oliver presumed him dead all these years. Mercer seemed to not want to have anything to do with Dr. Oliver and brushed him off repeatly. Mercer was Trent's father. He took Trent in when his parents died while working with him. He was a very strict yet loving father. He despised Trent's obsession with drawing. Mesogog planned to use the White Dino gem against the Rangers. But Trent unwittingly became bonded with its powers. When Trent became the evil White Ranger his relationship with Mercer was strained.  Mercer took over for Dr. Oliver's classes when Oliver became stuck in his morphed form.  He was trying to find away to free himself from his Mesogog alter ego. When Trent jioned up with Mesogog ,Anton made it clear to Trent that he wanted him to be good. When Mesagog tried to punish Trent for his betrayal, Anton remerged and saved his son. Trent became free of the evil power in the proccess. Mercer continued to try find away to get rid of Mesogog. He didn't want Trent to tell the Rangers an felt he could eventually handle the situation. Mercer ended his teaching duties when Oliver was able to return to his class.  Mesogog lost Zeltax and was adament that he had to be destoyed. Mesogog knew he needed to  get rid of Mercer soon ( and vice virsa).  Mercer became very desparate himself to get rid of Mercer. After being bretrayed by Elsa his secret was let out to the Rangers. Mesogog came down hard on Elsa but found away to split himself from Mercer entirly. Trent was able to rescue Mercer as the Rangers destoryed Mesogog's weapon ( the weapon had the power to turn humans into dinosuar mutants). Mesogog survived and used the energy he absorbed from the dino gems to obtain a more powerful form. The Rangers used all the powers in their gems to distory the villain. Mercer celebrated with the Rangers at the prom. He approved Trent's descion to go to Art School in the fall.

Elsa was one of  Mesogog's main servants. She was very loyal to her master. She loved to insult and torment her enemies. Elsa was also  Principal Randal. As Principal Randal, Elsa showed that she doesn't like kids. She gave the Rangers a hard time on their first day of classes. She tried to get close to Dr. Oliver, in order to find a way to defeat him for Mesogog.  She tried to trick the Rangers with a false dino egg and unleashed the Stegazord on the city. The Rangers were able to reprogram the zord to their side. Elsa gave herself a new look with longer hair. When Zeltrax left Mesogog's forces, Elsa became his  main general. She continued to come up with evil plans to take down the Rangers. Mesogog began to grow weary of her constant failures. Randal  took a card from Ethan since it was against school rules to play cards. Oliver went to talk to her about given the card as Randal morphed into Elsa. Her identiy revealed Elsa fleed the scene and turned the card into a monster. The monster was defeated and Mesogog was not pleased. Elsa planeted the card on Mercer in an attempt to force him to reveal his idenity (fearful Mesogog would get rid of her if she didn't strike at him first). The plan worked but Mesogog punished Elsa for the betrayal. Elsa tried to regain Mesogog's good graces but only ended up being used as energy for Mesogog's new device. This caused Elsa to revert to her civilian form. The Rangers found her and she later was able remember all the evil she had done. She told the Rangers Mesogog had her under his control the whole time. Zeltrax distoryed the Rangers lab and took Elsa hostage. The Rangers were able to save her. With all the evil defeated Elsa celebrated with the Rangers at the Prom.  Set to remain Principal of Reefside.

Zeltrax was another one of Mesagog's main warriors He was very loyal to his master and would stop at nothing to please him. He seemed to have a vendetta against Dr. Oliver. He was attracted to Elsa. Zeltrax always challenged Oliver but was always badly beaten in the end. He once created a clone of himself called Golden Rod. Golden Rod was eventually defeated by the Rangers. Eventually Zeltrax revealed that he was actuallty one of Oliver's old rivals (named Terrance Smith). Tommy got the job with Anton Mercer over him. After a lab accident Smitty was rebulit into Zeltrax by Mesagog . Zeltrax turned Trent in when he tried o overthrow Mesagog. Trent jioned Mesagog's armies and continues to annoy Zeltrax. Zeltrax lost a battle to him ( a battle that decided who was to be second in command to Mesagog). Later was quick to piont out when Trent bretayed his master. When Trent became good and jioned the other rangers Zelrax made a evil clone of him. Zeltrax also made a monster from the evil clone but saw it distroyed. He tried using a powerful flying machine and centepede robot against the Rangers, The Rangers foiled his plans and Olvie rejioned him in a clamatic battle. Oliver destoyed Zeltrax in the proccess. Zeltrac actually surviived and his nector from a powerful tree to upgrade his form. Conner used his new mega battle to defeat Zeltrax. Zeltrax reverted to his old form refusing to rejion with Mesogog. Mesogog wanted his old general distoryed.  Zeltrax returned yet again (with a new power up), taking the civilan Elsa prisoner. the Rangers saved Elsa but Zeltrax followed them back to base. While they were gone on a mission Zeltrax distoryed their lab and took Elsa hostage. The Rangers faced his new Zelzord. Oliver and Kira saved Elsa from Zeltrax. The Rangers self distructed the Mezadon Megazord and Thundersuarus Megazord to destory Zelzord. Kira and Tommy than finished Zeltrax for good.

Triptoids were additional foot soldiers of Mesogog. They were originally characters in a game Ethan got stuck in with Kira. When the two were freed the Triptiods followed them. Zeltrax recruited them for Mesogog. When Zeltrax went on his own the Triptiods worked for him. They are assumed destoryed now.

Fossilador

Fossilador was once created by Mercer and Oliver. He had the power to control people's minds. He was shut down when ghe got out of control. Folliador was stored in Mercer's lab. He was able to take control of Kira and made her restore him. He than discarded her and attacked the Rangers, Kira jioned her friends to destory the rogue mutation.

Copyotter

Copyotter was one of Mesogog's  monsters that he created from the geo randomizer. He had the power to make copies of people. The Rangers outsmarted him and defeated him. Pieces of him were used to create the White Ranger Clone.

Mad Mad Makerel

Mad Mad Makeral was created from the gentle Marrty ( an actor on a kids show). Mackeral had the power to capture people and turn them into bait. The Rangers freed the innocent people and destoryed Makeral. This  reverted him back to  Marty.

Jade Gladiator

Jade Gladiator was created from one of Mercer's ground breaking plants. Mesogog turned  into a monster. This monster gave the Rangers a huge challenge. It was defeated by the  combination of all the zords into one.

Lothor escaped the Abyss of Evill and took control of the Wind Rangers with tainted morphers. He teamed up with mesogog to take down the Dino Thunder Rangers. The Wind Ninjas were freed and jioned by Cam and the Thunders. They all teamed with the DinoThunder Rangers to take down Lothor and Mesogog's forces. Mesogog was angered at the defeat and fought Lothor. He turned him into one of his specimens.  

Zurgane returned from the Abyss of Evil to help Lothor. He was defeated by the Ninja Storm and DinoThunder Rangers.