Fate Averruncus, also called Tertium is a mysterious and extremely powerful child mage, who is the first and foremost rival to Negi Springfield. He first appears during the Kyoto School-trip Arc, as a mercenary, but his goal and identity remained unknown. Fate later reappears as the primary antagonist in the Mundus Magicus Arc; where his past and his objectives are unveiled little by little. He looks human but he is in fact a construct, more akin to a magical homunculus. He describes himself as a "mere doll".
As of the start of Return To Old World Arc, Fate is now one of Negi's allies and a teacher at Mahora.
Eight years after the war and Primum'sdeath, Filius Zectwoke Tertium up and put him under the command of Secundum so that he could continue Cosmo Entelecheia's mission of saving Mundus Magicus. After working with Secundum, Septendecim and Nii for a while they finally ran into Nagi.
Tertium asked him why they kept fighting when it was useless and Nagi answered that they hadn't given up on humanity, like Tertium and his team had. After the fight, which Cosmo Entelecheia lost, they returned to their base where Secundum started complaining about his loss. This prompted Tertium to ask him why he was so enthusiastic, since they were created from the same base model and he found it strange, causing Secundum to tell him that was normal to put all of your heart and blood into their mission and that he should get their master to recalibrate him since his lack of enthusiasm was an apparent defect.
While flying and thinking about Cosmo Entelecheia's mission Tertium's core started to fail and he fell from the sky. When he woke up, he was lying on a bed and was greeted by a young Shiori and her older sister.
It took him three days to recover, during which he discovers that he loves Shiori/Luna's sister's coffee.
Upon leaving, he promises to return one day and return the favor, at which Tertium is promised more of the coffee he loves. Tertium inquires of Zect regarding his malfunction and learns that he had never been programmed with purpose or even loyalty to the cause, thus the reason for his malfunction.
When Tertium returned sometime later, he finds that Shiori/Luna's village had been attacked and that she and her older sister had been grievously injured. Secundum rewrites Shiori's sister with the Code of the Lifemaker and is about to erase Shiori when Tertium beheads him. Secundum says that what he did to Shiori's sister is the fate of all their kind and Tertium promises to continue the mission, but laments not being able to drink Shiori's sister's coffee any more.
He is reprised by Chris Patton in the English dub and Akira Ishida in the Japanese dub.