Sentinel robots are perhaps the X-Men’s most persistent and prevalent threat in Marvel Comics and in Marvel’s animated and live-action adaptations.

Throughout most of Marvel’s animated and live-action X-Men projects, different kinds of Sentinel robots have posed a persistent threat to the X-Men team and mutantkind as a whole. First seen in Marvel Comics’ The X-Men #14 in 1965, Sentinels are massive humanoid robots that have been programmed to locate, capture, and sometimes even kill mutants. Originally created by military scientist Bolivar Trask, the Sentinel robots have evolved over the years to present a significant danger to mutantkind, with their simple task making them an easy antagonist to adapt for Marvel’s X-Men projects, and they’ll likely appear in the MCU, too.

The most prominent adaptations of Marvel Comics’ Sentinel robots have been seen in X-Men: The Animated Series, which ran for five seasons between 1992 and 1997, and 20th Century Fox’s live-action X-Men franchise, which released between 2000 and 2020. More recently, Marvel Studios Animation’s X-Men ’97 has also featured various different versions of Sentinels, with one terrifying Sentinel villain having been set up as a primary antagonist of X-Men ’97 season 1. Sentinels may have already been teased for the MCU, suggesting they may also be featured as an ever-present threat to mutants in Marvel Studios’ X-Men reboot and beyond.

10. X-Men: The Last Stand’s Danger Room Sentinels

X-Men: The Last Stand’s Sentinels Were Danger Room Simulations

While the Sentinels were originally planned to make their live-action debut in 2000’s X-Men, the robots were ultimately written out of the project. This meant their first live-action appearance occurred in 2006’s X-Men: The Last Stand, which opened with the established X-Men team training new members in the Danger Room. These Sentinels posed little danger, as they were simply Danger Room simulations, but this helped to display the sheer scale of these terrifying villains, as these Sentinels were enormous.

The Danger Room’s Sentinels Reappeared In X-Men: Apocalypse

2016’s X-Men: Apocalypse also featured Sentinels as antagonists in a Danger Room training simulation, though these were different to X-Men: The Last Stand’s. These Sentinels were the same design as those created by Peter Dinklage’s Bolivar Trask in 2014’s X-Men: Days of Future Past, helping to establish a sense of continuity in Fox’s revised X-Men timeline. X-Men: Apocalypse only provided a brief glimpse at these Sentinels, and they weren’t seen again.

9. X-Men: Days Of Future Past’s Mark I Sentinels In 1973

Bolivar Trask Created The Sentinels In 1973

2014’s X-Men: Days of Future Past provided the clearest look at 20th Century Fox’s Sentinel robots, and showed how they evolved over several decades. In the movie’s 1973 timeline, the creation of the Sentinels was explored, with Bolivar Trask hoping to use his giant robots to eliminate the apparent mutant threat. These Sentinels were made of space-age polymers and fitted with various weapons capable of killing mutants, though Trask wanted to continue experimenting to advance his designs.

The X-Men Stopped The Sentinels Ever Being Mass-Produced

At President Nixon’s unveiling of the Sentinels, Magneto assumed control of the robots and threatened Nixon and Trask’s lives. Had he been successful, the Sentinel program would have been greenlit, and the future war would have prevailed. However, Mystique thwarted Magneto’s plans, and the fact that a mutant saved the President convinced government officials to cancel the Sentinel program before it had even begun, saving the future and building some trust with humanity.

8. X-Men: Days Of Future Past’s Mark X Sentinels In 2023

Sentinels Subjugated Mutants In X-Men Days Of Future Past’s Dystopian Future

In the original timeline of X-Men: Days of Future Past, Mystique murdered Bolivar Trask, convincing the government to continue with the Sentinel program as originally planned. This eventually led to advancements being made with the Sentinels that saw them begin to target humans who had the potential of bearing mutant children, culminating in a dystopian future where humans and mutants were subjugated alike. These Mark X Sentinels were very powerful, and were only eliminated by Wolverine’s actions in the past.

X-Men: Days Of Future Past’s Sentinels Were Incredibly Powerful

Unlike their Mark I ancestors, the Mark X Sentinels in X-Men: Days of Future Past had a huge array of other abilities. Most notably, the integration of Mystique’s shape-shifting DNA into the Sentinels’ system meant that the robots could adapt their bodies to copy any mutant ability. This meant that the Sentinels could easily take on the likes of Iceman, Sunspot, and Colossus, making them incredibly terrifying and practically unstoppable.

7. X-Men: The Animated Series & X-Men ’97’s Sentinels

Sentinels Are An Ever-Present Threat In X-Men’s Animated Shows

Prior to 20th Century Fox’s development of the live-action X-Men franchise, Marvel introduced the Sentinels as a persistent threat in X-Men: The Animated Series. In fact, Sentinels were the first antagonists the X-Men faced in X-Men: The Animated Series’ double-premiere, “Night of the Sentinels,” back in 1992. These Sentinels were originally controlled by Bolivar Trask and Henry Peter Gyrich before the program was canceled and relocated to Genosha, where the Master Mold took over.

X-Men: The Animated Series’ Sentinels Were Very Comic-Accurate

The version of the Sentinel robots seen in X-Men: The Animated Series, and, more recently, in X-Men ’97, are much more comic-accurate than those depicted in Fox’s X-Men franchise. These Sentinels look much more like the humanoid robots from Marvel Comics, with their accurate red-and-purple bodies towering over buildings and trees. This makes them a very imposing threat, though it’s no wonder this design was changed for live-action adaptations, as they don’t look all too realistic.

6. Master Mold

Master Mold Is A Sentinel Factory In X-Men: The Animated Series

Similarly to the Sentinels themselves, Master Mold was also created by Bolivar Trask, but is a much larger version of his robots. The Master Mold is a factory that is capable of building thousands of smaller Sentinels at will, but, in X-Men: The Animated Series, the Master Mold soon began targeting mutants and humans alike. The X-Men battled Master Mold several times, with the villain eventually being destroyed, except for his head. Master Mold’s head was later destroyed by Morph, marking the end of the villain’s story.

Master Mold Returned In X-Men ’97’s Premiere Episode

While the Master Mold was well-and-truly eliminated in X-Men: The Animated Series, the iconic villain did make a reappearance in X-Men ’97’s premiere, “To Me, My X-Men.” This version was non-sentient, however, and was easily destroyed by the X-Men during their battle against Bolivar Trask and other Sentinels in a Saharan junkyard. Of course, however, Master Mold could return in the live-action MCU.

5. Nimrod

Nimrod Is An Advanced Sentinel From 2055

Nimrod was introduced in X-Men: The Animated Series’ adaptation of Marvel Comics’ Days of Future Past event, debuting as a super-advanced Sentinel from the dystopian future of 2055. Nimrod followed Bishop back through time on his journey to change history, and posed a significant threat to the X-Men, thanks to his ability to self-repair and adapt his form. Nimrod formed the inspiration behind X-Men: Days of Future Past’s Mark X Sentinels, and was similarly as dangerous.

Nimrod came from the Days of Future Past timeline in Marvel Comics, but wasn’t included in Fox’s live-action adaptation of the storyline.

Nimrod Is Also Important To X-Men ’97

Nimrod hasn’t been seen since X-Men: The Animated Series season 4’s double-episode, “One Man’s Worth,” in 1995, in which he traveled back in time to kill Professor X before he could form the X-Men. Nevertheless, the advanced Sentinel also poses a huge danger in X-Men ’97, as the series’ overarching villain, Bastion, is an evolution of Nimrod, and Nimrod appeared in the opening credits of X-Men ’97 episode 7, “Bright Eyes,” teasing his return.

4. X-Men ’97’s Wild Sentinel

The Wild Sentinel Attacked Genosha In X-Men ’97 Episode 5

X-Men ’97 episode 5, “Remember It,” took inspiration from Marvel Comics’ epic E is for Extinction storyline from 2001, exploring a devastating attack on the mutant nation of Genosha. In X-Men ’97, Mister Sinister used Bolivar Trask’s DNA to assume control of a Wild Sentinel to carry out this attack, and this was very effective. The three-headed Wild Sentinel, which looked more like an insect than the humanoid Sentinel robots, caused widespread destruction on Genosha, and caused the deaths of hundreds or thousands of mutants.

How Was The Wild Sentinel Defeated In X-Men ’97?

While the only X-Men present on Genosha at the time of the attack were Magneto, Rogue, and Gambit, the trio put up a strong fight against the Wild Sentinel. After Magneto was seemingly killed, Gambit saved Rogue’s life, though was impaled by the Sentinel. In his final moments, Gambit supercharged the Wild Sentinel and blew the creature to smithereens, tragically sacrificing himself in the process.

3. X-Men ’97’s Prime Sentinels

Prime Sentinels Are New Versions Designed By Bastion In X-Men ’97

In the aftermath of the attack on Genosha, X-Men ’97 episode 7 saw Rogue and the X-Men searching for Bolivar Trask. Upon finding him, however, the team also realized that brand-new Prime Sentinels had been created. In Marvel Comics, the Prime Sentinels were created by Bastion during 1997’s Operation: Zero Tolerance event, which included him enhancing regular humans with cybernetic implants that would transform them into Sentinels in the presence of mutants. These Sentinels are a harrowing addition to X-Men ’97.

X-Men ’97’s Prime Sentinels Are A Terrifying Prospect

The fact that X-Men ’97 introduced Prime Sentinels in the lead-up to season 1’s highly-anticipated three-part finale suggests that some notable characters may be revealed to be Sentinel sleeper agents. This could mean many allies to the X-Men will become enemies, perhaps including the likes of Valerie Cooper and Moira MacTaggert. This has even already been seen in X-Men ’97, as Bolivar Trask became a Sentinel in episode 7.

2. Bolivar Trask’s Human Sentinel Zombie

Bolivar Trask Is Resurrected As A Sentinel In X-Men ’97 Episode 7

The X-Men found Bolivar Trask in X-Men ’97 episode 7 in the midst of Rogue’s rampage across the United States. Unfortunately, this meant that Rogue had no qualms about simply dropping Trask from the top of a building, killing the long-running X-Men villain. Unbeknownst to the X-Men, however, Trask had already been turned into a Prime Sentinel, which allowed him to be resurrected as a powerful mutant-killing machine. This proved just how dangerous the Prime Sentinels can be in X-Men ’97 season 1’s finale.

Rogue Broke The X-Men’s Number 1 Rule By Killing Bolivar Trask

Rogue’s actions in X-Men ’97 episode 7 were far from uncharacteristic for the former Brotherhood of Mutants member, but still came as a shock to the rest of the X-Men. The cardinal rule of being an X-Man is a simple no-kill policy, but Rogue willingly broke this rule by dropping Trask to his death. The repercussions of this will surely be felt for years to come.

1. Bastion

Bastion Is A Humanoid Combination Of Master Mold & Nimrod

X-Men ’97 episode 7 finally revealed Bastion to be the series’ overarching antagonist. Introduced in Marvel Comics’ X-Men #52 in 1996, Bastion is the fusion of Master Mold and Nimrod after the pair were thrust into the Siege Perilous, a mystical crystal. This combination created a powerful human-looking Sentinel, who became Sebastion Gilberti, with no memory of his true origin, though his Sentinel body meant that his hatred for mutants still developed.

Bastion Has Been Hiding In The Background Of X-Men ’97 Since The Beginning

Beau DeMayo, X-Men ’97’s creator, confirmed Bastion had made appearances throughout the series before episode 7 (via Twitter). Bastion was a mutant buyer in episode 1, appeared next to Valerie Cooper in the war room in episode 2, showed up in a photograph with Forge in episode 4, and briefly appeared at the gala in episode 5. This suggests Bastion has been manipulating things all along, so poses a massive threat to the X-Men in the series finale.