A member of Mammoth Mogul's Order of Ixis, Agunus survived the destruction of his order along with fellow mages Nusgau and Suguna. The three joined forces after their Order's destruction, and after teaching each other their respective magicks, they set out to capture control over the element of fire by making contact with the sun. Despite their cooperation, Agunus held back part of his knowledge regarding earth, and so thought to surpass the others by reaching the sun first. However, he made the mistake of betraying the others first and the other two both copied his trick. When Nusgau made his bid to take the lead, Agunus grabbed Nusgau, and Suguna grabbed Agunus and they all fell into the sun together, fusing them together into Ixis Naugus. (StH: #66, #163)
The rhino geomancer and his fellow Ixian wizards were awoken decades later by the effects of Operation: Clean Sweep, and though Naugus fought back the three sorcerers' bids for control of his body the rhino and his brethren remained in the back of the hybrid's mind. Although intent on claiming control of Naugus, the trio would aid him by providing advice as he attempted to win over the people of New Mobotropolis. Agunus and his cohorts continued to torment Naugus as he sought to discredit Team Freedom, eliminate Elias Acorn by secretly contacting Dr. Eggman, and further secure his hold over the Republic of Acorn by creating a Ritual Chamber to augment his powers. With his power increased, Naugus' plan was to cast a spell that would enslave the entire city, allowing him to focus on dealing with his components. The influence of the three wizards also caused Naugus' body to undergo monstrous mutations that could only be maintained through the use of his Chaos Emerald.After the failure of Naugus' plan to enslave the city, Agunus and the others continued to berate him as he sought a host body, failing with both Maximillian Acorn and Jules Hedgehog. Agunus notably noticed Naugus' calm prior to a concert held by Mina Mongoose, though it was quickly shattered when Naugus realized that the will of the populace was against him. When Geoffrey St. John attempted to convince Naugus to change his ways, Agunus was opposed along with his compatriots, and were pleased when Naugus agreed with them. The fusion of the trio chose instead to possess Geoffrey as a vessel, the Skunk having sworn loyalty to him years previously. (StH: #231, #232, #234, #236; SU: #41, #42, #43)
Like his fellow Ixians, Agunus is power-hungry and treacherous, with no qualms about betraying his associates. He is as eager as his two partners to return to full life, despite the objections of Ixis Naugus. His hatred for Naugus often leads him to mock the mutant wizard, though he is not above offering Naugus advice if he believes it can benefit his own interests.
Agunus was an elemental wizard who mastered the power of Earth, later gaining knowledge of manipulating Water and Wind from his comrades. Though he instructed the others in his elemental proficiency, Agunus held a part of is knowledge back. As his abilities have been absorbed into Ixis Naugus, Agunus is left as a spirit whom only Naugus and the others can perceive, though he retains the ability to mentally torment Naugus.
- Agunus's name is an anagram of the other two members' names and that of their combined form, Naugus.
- Ian Flynn revealed that Agunus and his compatriots were not actually participants in the Forgotten War, but became members of the Order later. 
- As a result of the events of Worlds Collide, it appears that Naugus is now a Troll rather than a creature born from the fusion of three Mobians; as such, it can be presumed that Agunus and his compatriots either never existed or else were never associated with Naugus.