Sentinel Zeta Prime was not one of the Thirteen, but he ruled since near that time. It is believed he was born Zeta, was later dubbed Sentinel Zeta and later became Sentinel Zeta Prime. When the Quintessons ruled Cybertron during the Age of Wrath, Sentinel led the rebellion against them.
He was successful and Cybertron entered its Golden Age of Space Bridges and expansion. Cybertronians expanded to worlds such as Velocitron, Gigantion and the Hub. Trypticon Space Station was also built. However, the Space Bridges became unreliable after some time and the Golden Age came to a close. To try and maintain order in society, Sentinel, at the High Council's nagging created the Caste System.
The Caste System functioned so that every Cybertronian that emerged from the Well of AllSparks was taught to transform, placed in a caste and given a name. Those in the lower caste, however, did not receive a name. Alpha Trion opposed this system and made his thoughts very clear to Sentinel, but eventually withdrew to the Hall of Records. After a while Sentinel became a hermit and said he did not care for the lower castes.
War for Cybertron
Later in his life a gladiator named Megatron began preaching against the Caste System. One night, Sentinel attended a performance at Altihex Casino and it was here the Decepticons attacked. Sentinel did not fight back as he relied on his bodyguards Starscream, Thundercracker and Skywarp to fight for him. Only to discover they were trying to get recruited into the Decepticon ranks and used him as a peace offering. Megatron used Sentinel as a punching bag, whenever his plans failed. He was later moved from Kaon to Moonbase One. Starsceam, wanting to rule the Decepticons, offered Sentinel a chance at redemption. He informed him that Megatron was trying to acquire the Plasma Energy Chamber and released him to confront Megatron. The two fought beneath Iacon, and though Megatron complimented his skills as a fighter, the gladiator literally disarmed the Prime. He saw the Code Key of Justice, which was needed to open the Chamber, inside of Sentinel.
Sentinel was shoved back into Kaon Prison. He was rescued by the Autobots. In his last moments of life, he spoke to his successor, Optimus Prime. He told him that he had overstayed his welcome as a Prime and that Optimus should be truer to the title than he was. His last request was that Optimus travel to the Core and remove the Dark Energon. His body was laid to rest in Iacon and Optimus was now truly all that remained of the once great civilization.
Sentinel's policies and attitudes left some Cybertronians with a bad taste towards Primes and outright refused to follow them, believing them corrupt and greedy. Some Decepticons disliked Optimus Prime solely for being Sentinel's successor.
Once the majority of Cyberton's people had left the planet, Swoop called dibs on living in Sentinel Prime's abandoned palace. Sadly, his request was denied and he lived with the rest of the Autobots.
- Transformers: War for Cybertron (DLC)
- Transformers: War for Cybertron (DS) (Non-Playable Character)
- Transformers: Fall of Cybertron (DLC)
- Transformers: Rise of the Dark Spark (Unlockable)
- Sentinel's title of Prime was and is still honorary.
- Prior to it being revealed that the arm belonged to Liege Maximo, many assumed it was Sentinel's arm.
- As revealed in the unlocked concept art in the Extras menu of the Transformers: War for Cybertron video game, some early colour schemes for War for Cybertron Zeta Prime resembled that of Generation 1 Sentinel Prime. Also revealed in the concept art is that Zeta Prime's vehicle mode is a Cybertronic car, though he doesn't actually transform in the course of the game.
- Since Exodus featured a Sentinel Prime and War for Cybertron featured a Zeta Prime, both occupying the same role, Hasbro suggested at BotCon 2010 that they were the same guy: "Sentinel Zeta Prime". However, the War for Cybertron comic also written by Alex Irvine refers to the disappearance of Sentinel as depicted in the novel, when Zeta Prime in the games doesn't go missing until much later than the novel portrays it. Yet, the comic portrays Sentinel Prime with Zeta Prime's appearance, in attempt to further enhance the connection between the two.
- Transformers Vault paves over the confusion by referring to "Sentinel" as a title, i.e. "sentinel, Zeta Prime".
- Zeta Prime became a playable character in multiplayer and Escalation mode as part of a DLC pack released on September 7, 2010. He was available for the Xbox 360 and PS3 versions of the game, but not for the PC version. He is a member of the Leader class and transforms into the vehicle mode shown in his concept art. His character model in multiplayer is designated the Elite Rig.
- In the game, Zeta Prime appears to share exactly the same character model as the head member of the Autobot High Council.
- In Exodus, Sentinel Prime's belt has the sigil of Vector Prime. However, in War for Cybertron, he doesn't seem to wear a belt at all.
- A Sentinel Zeta figure by Reysol Grant won a Collectors' Club custom figure contest, announced in Hasbro Transformers Collectors' Club issue 37.
- The dead Prime seen in the Transformers: Prime episode "Alpha/Omega", whose arm was harvested by Megatron so that he could use the Forge of Solus Prime, was identified as Sentinel by The Art of Prime, but that doesn't make sense, since Sentinel was not a true Prime and as such his limb would not have conveyed the power Megatron sought. The concurrently-published Covenant of Primus identifies it as the Liege Maximo.
- Sentinel Prime never made a physical appearance or was mentioned in Transformers Prime. Sentinel Prime only appeared in the live action movie, Transformers: Dark Of The Moon as an antagonist. In the movie, Sentinel Prime was Optimus Prime's mentor, while in Transformers Prime, Alpha Trion served as Optimus's mentor during the golden age on Cybertron.