The Clerics were a group of elite ThunderCats who served as royal guards to the King. They were sometimes also referred to as the Guardians of the Crown.
This group of Thunderans existed even during ancient times of Thundera's empire, they've always served the Lord of the ThunderCats. Most serve as wizards-in-training to the lead Cleric, who is also adviser to the king. They wear long white robes with a face-covering hood shaped as the head of a cat. This keeps their faces covered with only their eyes seen, and was used as a form of protection against attacks as well as keeping their identities secret. They had a natural talent for traveling at extremely high speeds which made them a devastating foe to face as they were able knock down armies incredibly quickly.
When factions threatened to take the Book of Omens, the Clerics were charged with taking it to safety and travelled to parts far beyond the ThunderCats domain. They ultimately hid it in a place only they knew and crafted the magical Tower of Omens as a resting place for it. Thus, the Book of Omens became hidden for centuries on Third Earth. The secrets and leadership of the Clerics would eventually go into the hands of Jaga. In the reign of Claudus, the Clerics were assembled when Lion-O was to receive the Sword of Omens.
By later era, the undead being known as Mumm-Ra was freed from his slumber by the actions of Grune. Following his release, he worked with Grune and assembled an army of Lizards to assault Thundera during the reign of Claudus. Whilst the ThunderCats were overwhelmed by the army of Lizards who were equipped with advanced technology, the timely arrival of the Clerics seemed to had turned the tide of battle. However, Mumm-Ra who had disguised himself as Panthro revealed his true form. The moment that Jaga had always feared came to pass and he ushered his Clerics to battle to the death. However, Mumm-Ra killed all the Clerics at the scene with the exception of Cheetara who saved Jaga's life.
Cheetara would become one of the few Clerics left and charged with accompanying Lion-O in finding the Book of Omens. As they searched for the Tower of Omens, she explained the history of the Clerics' involvement in hiding the Book in distant times.
- The Sword of Omens (episode)
- Ancient Spirits of Evil (episode)
- Journey to the Tower of Omens
- Into The Astral Plane