Despite his imposing stature and appearance, Omnitraxus Prime is friendly and somewhat goofy toward those in need of his help. Calling himself the "space-time guy", he is willing to assist people with space-time-related problems. However, he can be serious if the situation requires it, as demonstrated when he explains the gravity of Star's problem in "Mathmagic".
Omnitraxus first appears in "Page Turner" as a member of the Magic High Commission. He is unable to be in the Commission's office in person during their meeting with Glossaryck, so they communicate with him via crystal ball. Unfortunately, the other Commission members are unable to hear him due to the crystal ball's poor reception.
He has a major starring role in "Mathmagic". When Star Butterfly becomes trapped in a time loop and Father Time is unable to help her, Omnitraxus appears before her and gives her advice on how to break the loop. He takes Star inside his body, where she is able to observe numerous alternate versions of herself from other universes. With Omni's advice, Star manages to break the time loop and stop all of time and space from collapsing. Omnitraxus notes that his mastery over "space-time", which covers time loops, is distinct from Father Time's mastery over "time-time".
In "Face the Music", Omnitraxus and the rest of the Commission attend Star's "Song Day" ceremony. After the song reveals that Glossaryck and the Magic Instruction Book were taken by Ludo, he and the rest of the Commission are left shocked and outraged at Queen Butterfly for keeping that information from them.
In "Starcrushed", Omnitraxus takes part in a mission to recover Glossaryck and the book of spells from Ludo. Before he can engage Toffee in battle as he speaks to him, Toffee absorbs his powers, reducing him to nothing but a skull face. Before Toffee can destroy them all, Queen Butterfly recovers his skull and escapes through a portal.
In "Return to Mewni", Omnitraxus is stated to be in stasis, and Star and Moon bring his and the rest of the Commission's bodies to the Magic Sanctuary in an effort to restore them. In "Moon the Undaunted", he appears in flashback as a member of Queen Moon's royal court, and is eventually rejuvenated in "Toffee".
In "Stranger Danger", he and the rest of the Commission capture the freed Eclipsa Butterfly, and examine Star to see if Star was affected by Eclipsa's "evil". In "Total Eclipsa the Moon", Omnitraxus and the rest of the Commission are seen rushing to the Bureaucracy of Magic's archive room after Moon accidentally triggers the alarm.
In "Butterfly Trap", Omnitraxus takes part in Eclipsa's trial, where it is revealed he and the rest of the High Commission orchestrated a conspiracy to replace Eclipsa's daughter Meteora on the throne with the peasant girl Festivia.
In "Divide", Omnitraxus and the Magic High Commission try to serve as advisors for acting queen Star, but Star dismisses them for their deception toward the Butterfly family.