The Sentinels are a group of supervillains who first appeared in Marvel Comics X-Men (Vol. 1) #14.

Sentinels are titanic semi-humanoid robots designed to locate and either capture or kill superhuman mutants. As a fleet of robotic killing machines, Sentinels do not fit the regular mold of a supervillain. They are emotionless, soulless, unindividualized killers, slaves to their prime directive: kill mutants. They have been used repeatedly by many different parties under the pretence of both good and evil, but they always perform their task without mercy. They are relentless death personified in giant robot form. They are also my favorite comic book villains. The unique threat of an essentially unstopping and undying group of enemies creates a desperate and gritty tone in the stories that feature Sentinels. They are truly horrifying, always commanding compliance in cold metallic voices: FREEZE MUTANT!

Sentinels have appeared in several different forms over the years. They are separated into generations using the Mark notation. Various unique Sentinels, like the time traveling Nimrod, the titanic Master Mold, the insidious Prime Sentinels and the short-lived Tri-Sentinel have also plagued the heroes of the Marvel Universe. In order to structure the history a bit, the discussion will be divided by Mark notation.

Mark I Sentinels

Originally created by famed genius anthropologist Bolivar Trask, the Sentinels were the result of one man's fear and hatred. Trask had dedicated his life to the study of man's evolution. Noting that some superhumans emerging in the world where in fact human mutations, Trask dedicated his studies to this fantastic new branch of mankind. Trask soon discovered that his young son, Lawrence, developed precognitive abilities after hitting puberty. Horrified, Trask slowly formed his paranoid vision: these mutants where the first of a newly evolving branch of mankind, which he dubbed Homo Superior, which would use their powers to dominate the world and enslave mankind. The example of Magneto and other mutant supervillains cemented this view in Trask's mind. Trask founded a group of researchers which he lead with his son, to compile evidence that showed mutants posed the single greatest threat to humanity in existence. Using his fame and large fortune, Trask formed a large team of cyberneticists, roboticists and engineers to realize his designs for the ultimate solution to what he perceived as a global dilemma: The Sentinels.

Mark I Sentinels were 20-foot tall humanoid robots, possessing great strength, built to be immune to gas, psionics,energy and physical attacks. Able to operate anywhere on earth or in the vacuum of space, they were inescapable. Capable of flight via boot jets, protected with thick metal armor and armed with a variety of different energy and force projection weapons which they could fire from their chests, they were formidable. Possessing a wide array of sensors that could scan all living beings within their vicinity and detect mutation, they were infallible. Trask's Sentinels were designed to be humanity's solution to the mutant problem: mass-produced death.

Trask publicly revealed the existence of the Sentinels in the course of live televised debate on the subject of the "mutant menace". The man Trask faced in his debate was Professor Charles Xavier, secretly a mutant and the leader of the X-Men, a group of mutants fighting to protect humanity. Trask then unleashed his fleet of Sentinels on the world.

The Sentinels, newly released and relying on their programming for the first time came to a purely logical conclusion: In order to protect humanity from mutants, they should take control of society from "imperfect" humans. Trask tried to order his robots to obey, but they kidnapped him and returned him to the fortress he had constructed for the Sentinels headquarters. The X-Men, also freshly captured, were being held captive. The principal Sentinel, known as the Master Mold, tried to force Trask to construct an army of more Sentinels so that they could complete their program of conquering the human race. Using a mind reading device of his own creation on the X-Man called Beast, Trask discovered the truth. Finding that not all mutants where evil, and that he had created a greater threat to humanity, Trask sacrificed his life in destroying the Master Mold. Most of the other Mark I Sentinels were also destroyed in the ensuing explosion.

Mark II Sentinels

Mark II Sentinels were some of the most powerful Sentinels ever devised. Lawrence Trask, seeking to avenge his fathers death at what he saw as the X-Men's meddling, worked feverishly from his father's notes to design a more powerful Sentinel. Larry was himself a mutant, but his father had designed a medallion that operated to suppress his mutant abilities. Larry reused the remains of the destroyed Mk. Is, as well as constructing many new Sentinels. The Mark IIs were lead by Number Two, the Sentinel which acted as the decision maker for the entire fleet. The younger Trask was careful not to repeat his father’s mistake in giving the robots too much autonomy. Larry could control the robots wearing a special cybernetic helmet.

The Mark II Sentinels were constructed along lines similar to the Mark I, with increased capabilities in flight, mutant detection, armor, and weaponry. In particular, the Mark II had gas jets and steel tendrils in their hands that could emit a powerful knockout gas and entangle opponents. They were also able to adapt to almost any form of attack and counter it. Information on a defense was relayed to all fellow Sentinels and retained indefinitely. They could also regenerate damage due to internal self-repair facilities and adapt their own programming.

Larry Trask unleashed Sentinels in the same manner that his father did. While he was unleashing his fleet, the medallion that suppressed his powers was accidentally removed. The Sentinels realized that he was a mutant and declared their autonomy. Number Two assumed command. While battling the X-Men, the cold logic of Number Two concluded that that the best way to halt human evolution was to destroy the main source of mutation-inducing radiation: The Sun.

Arriving in solar orbit, the Sentinels concluded that they lacked the means to actually destroy the Sun. A new method of attacking the mutant problem need to be devised. While calculating the next step, the solar heat and radiation caused Number Two to "mutate" itself. Gaining the power to teleport and overcoming the restrictions against killing humans in its program, Number Two led the Sentinels back to the Great Australian Desert. In the desert, they developed a way of triggering massive solar flares. The intent was to use the flares to sterilize humanity, thus preventing mutants from being born. Once this was accomplished an artificially created race incapable of mutation would be created. The Avengers battled and defeated the Mk. IIs to halt their horrible plan, and all of the Sentinels were deactivated or destroyed, and buried within a mound in the desert. Larry Trask was killed during this final battle.

Mark III Sentinels

Following the death of Larry Trask, and recognizing the threat of private ownership of massive killing machines, the plans for the Sentinels came under the control of the United States government. Seeing that Bolivar and Larry Trask had been concerned about the rise of superhuman mutants, a federal investigation headed Dr. Steven Lang was commissioned. Its task: discover how mutations bestowing superhuman powers came about. Unbeknownst to his employers, Lang, like the Trasks, was a fanatical mutant hater. Seeing his opportunity, he used his mandate to gain access to the Trask notes and designs, and then approached the Hellfire Club, an elite social organization of the world's wealthiest and most powerful figures. Seeing Lang as a potential tool in its pursuit of world domination, they provided Lang with the money he needed to construct new Sentinels, and even went so far as to construct a space station to be used as a headquarters. The Hellfire Club's largely mutant membership was unaware that Lang's real intention was to kill every superhumanly powered mutant he captured. Lang in turn was unaware that the Hellfire Club was headed by a group of mutants bent on world domination.

Mark III Sentinels were inferior to those constructed by the Trasks. The notes Lang worked from were incomplete, and the secrecy surrounding his activities hampered his activities. Trying to ensure that these Sentinels could never rebel against him, Lang make them less intelligent and adaptable than their predecessors. Like the Mark Is, the Mk. IIIs had great strength, could fly using jets in their feet, and could fire energy beams. They could also generate a protective life support bubble that could hold up to six human-sized life forms, allowing them to be transported through space. As a strange side project, Lang made several Sentinels that resembled the original five members of the X-Men.

Lang's Sentinels where sent out to collect mutants for study and termination. Unfortunately for Lang, his first captives were the superhero team the X-Men. The ensuing battle destroyed the space station and the Mark III Sentinels. Lang was left a mindless vegetable, although he had imprinted his brain patterns in the computer of the 30-foot tall Mark III Master Mold. Master Mold then attempted to continue Lang's mission, but it was defeated by the monstrous Incredible Hulk and left for dead.

Mark IV, V, VI Sentinels

After the terrorist organization called the Brotherhood of Evil Mutants attempted to assassinate Senator Robert Kelly, who was undertaking a public investigation of the possible menace posed by superhumanly powerful beings, the Office of the President authorized the secret and illegal operation known as Project Wideawake.The Project's mandate was to investigate, and if need be capture, any superhumanly powerful mutant who the project assessed to be a threat to national security. The director of the project was special agent Henry Peter Gyrich of the National Security Council. Senator Kelly, personally interested after his assassination attempt, was a special consultant to the Project. Sebastian Shaw, secretly a mutant and a member of the Hellfire Club, joined the project after the government contracted Shaw Industries to construct Sentinels in secret.

Shaw Industries was licensed by the government under heavy secrecy to construct Sentinels for use by Project Wideawake and by the Department of Defense. Shaw produced three models of Sentinels, Mark IV, V & VI, with new design modifications. Without the government's knowledge, Shaw used these government financed Sentinels to attack the X-Men in his role as leader of the Hellfire Club. Having the government pay his company to provide him with the tools he needed to conquer the work was Shaw's personal windfall. The X-men defeated the Sentinels used by Shaw and forced the cancellation of the Project, relegating the government's Sentinel fleet into storage. Whether or not Shaw Industries continues to work in secret is not known.

The three marks of Sentinel produced by Shaw Industries where all very similar to the Mark II. The greatest difference between the generations was the load out of weapons available. All Shaw Marks included the special defensive learning program that shared learned tactics between Sentinels. This data could be analyzed to provide a Sentinel with special weaponry against a particular mutant. The Mark IV was famous for incorporating searchlight eyes for targeting and blinding opponents. Mark V Sentinels received the added ability of projecting liquid nitrogen from their eyes to encase opponents in a sheet of ice.

Just before the Prime Sentinel threat, the psychic being known as Onslaught activated most of the Sentinels that were in storage from Project Wideawake. He used them to help in attempting to seize control of New York City. The giant machines laid waste to part of the city and battled many hero teams, including the X-Men and the Avengers. With Onslaught's defeat, these Sentinels were presumably returned to government storage.

Omega Sentinels

Several other models of Sentinels were created in the futures of an alternate Earth. In one such alternate reality, the Brotherhood of Evil Mutants succeeded in assassinating Senator Robert Kelly. This future is shown in the Days of Future Past storyline. In this divergent reality, a presidential candidate gets elected on an extreme anti-mutant platform, and his administration unleashes the Project Wideawake Sentinels. The Sentinels fulfill their anti-mutant mandate by taking over North America, and killing or capturing virtually all superhuman beings, mutant or otherwise. Those not killed were incarcerated in mutant internment centers, which are little more than concentration camps.

During this time the Sentinels themselves created a new mark of Sentinel. The Omega series especially designed for hunting and killing superhuman targets, mutant or not. Like other Sentinels, they have tremendous strength are highly resistant to damage, and can fly using propulsion units in their feet. Omega Hunter-Killers are almost identical to the Mk. IV, differing only in improved weapons and abilities. Omega Sentinels contain self-repairing systems. Their modified capabilities include additional electrical insulation and huge steel darts that can be used as weapons. Omega Executive models have increased intelligence and an Encephalo-Scan sensory device that reads a target's brainwaves and determines if they are lying. Omega Sentinels are the ones shown terrorizing mutants in this alternate timeline. The New Mutants, a team of young superhuman mutants trained by Xavier, were temporarily transported into this nightmarish timeline where they faced several unique Omegas. One of these Sentinels was modular, having arms, legs and a torso that could separate and operate independently. They also painted themselves to resemble the costumes of slain heroes, like Captain America. The young mutants eventually escaped back into the present.

Nimrod, the Ultimate Sentinel

During the Sentinels' reign in this alternate reality, Project Nimrod created the most advanced version of a Sentinel robot possible using that reality's technology. The product of the project, Nimrod the Hunter, traveled back into to the reality where Kelly had not been assassinated, where it again hunted superhuman mutants.

The X-Men neutralized Nimrod, but his technology merged with that of the Mark I Master Mold. The new Nimrod/Master Mold combination then again battled the X-Men. The mutant superheroes where only able to defeat the robot by forcing it through the dimensional portal called the Siege Perilous. The threat of Nimrod was eliminated... for the time being.

The Tri-Sentinel

Another unique Sentinel was created by the Asgardian god of mischief, Loki, as a last defiant act of vengeance against various heroes of New York. The Tri-Sentinel, a magical merger of three prototype Sentinels created by Shaw Industries New York, was commanded to destroy a nuclear facility on Long Island, thereby destroying New York City. The six-armed three-faced Sentinel almost completed its deadly task. It was destroyed single-handedly by Spider-Man, who at the time wielded the cosmic powers of Captain Universe.

The Tri-Sentinel was later rebuilt by the Life Foundation in an attempt to replicate the robot for a state-of-the-art security force. Nova and Spider-Man fought the machine. They managed to get inside and then activated its fail-safe device. A shielded box containing Antarctic Vibranium was opened and the compound began melting the Sentinel's internal components. The Tri-Sentinel eventually overloaded and exploded.

Fitzroy's Future Sentinels

Again, another branch of reality produced unique Sentinels that return to plague the main timeline. A time-traveling mutant named Fitzroy came to the prime reality bringing Sentinels from his version of the future. Sentinels from Fitzroy’s time were designed to be a merger of Nimrod and Master Mold. Fitzroy used these Sentinels to destroy various people associated with the Hellfire Club. Fitzroy and his Sentinels were later defeated by the X-Men and the Hellfire Club.

Prime Sentinels

While battling the Nimrod/Master Mold robot, the X-Men forced the robot into a mysterious dimensional portal in order to defeat it. However, the magic of the Siege Perilous allows any entity that passes through it to be reborn as a new being. Nimrod/Master Mold returned in humanoid form as Bastion.

The android Bastion connected himself with covert factions within the United States government, similar to those who started Project Wideawake, initiated Operation Zero Tolerance. Using the combined knowledge of both Master Mold and Nimrod, Bastion created a new type of Sentinel. Prime Sentinels were actually humans who had been fitted with cybernetic nanotech implants which, upon activation, transformed the humans into armored beings with powerful weapons systems. These altered humans were set up as sleeper agents, unaware of their programming, which was awakened only by mutant activity in their immediate area.

Commanding this hidden army of Sentinels, he razed the X-Men's Westchester, New York mansion, downloading Xavier's extensive Cerebro computer files on mutants around the world. Bastion then used this information to systematically attack and capture the X-Men and their associates. The android ultimately was eventually defeated and destroyed by the X-Men with help from the government agency SHIELD, but they found it difficult to locate and deactivate all the humans that had been transformed. The mutant heroes could not attack these cyborg Sentinels in wanton fashion, as they were victimized humans, a weakness on which Bastion likely had counted. The destroyed Bastion was recovered later by the supervillain group the Acolytes and parts where used in creating the villain Template.

Neo-Adaptive Sentinels

The newest face of the Sentinel threat has seemingly begun to appear. A powerful creature calling itself Cassandra Nova Xavier used the remains of a Mark III Sentinel base in Ecuador to launch a hideous attack on mutantkind. Using its various powers, Nova located the base and Donald Trask, a relative of Bolivar Trask, original creator of the Sentinels. Ravaged by time and bent to the will of an inhuman creature, the strange Sentinels produced at the factory where of no standard template. Rusted parts, adapted materials and twisted forms where created and sent after mutants worldwide. Nova then killed Donald Trask and used his DNA signature to send three city sized Sentinels to attack the island nation of Genosha. X-men Wolverine and Cyclops tried to stop her and failed, capturing her only after the attack was sent. The twisted parodies made a kamikaze attack on the island, using nuclear warheads. The entire country of Genosha was obliterated. 16 million mutants, including Magneto, died in the assault.

Apparently separate from Nova's twisted creations, smaller human-sized robots of different designs and capabilities have made continuing attacks on mutants in the Chicago area. Employing the Sentinel methods of adapt and overcome, as well as sharing tactics, these mutant hunters seem to be the next generation of the Sentinel threat.

A Boy and his Sentinel

Juston Seyfert, a teenager from Antigo, Wisconsin, recently discovered the remains of a Mark VI Sentinel scattered across his father's scrapyard. Likely destroyed during Onslaught's attack on New York City, the machine was severely damaged and blown into many small pieces. A social outcast at school, Seyfert has taken it upon himself to reconstruct the massive engine of destruction for his own purposes. What kid wouldn't love to have a massive robot to play with? Whether or not this will be a good idea or not remains to be seen. This concept will be explored in a new monthly series from Marvel starting in April 2003, entitled Sentinel.

SCANNING... MUTANT DETECTED!

Where and when the Sentinels will return is not immediately known, but the effects of their existence are still felt by the heroes of the Marvel Universe. Prime Sentinels still lurk undetected, the fleet created for Project Wideawake waits in storage and the forces amassed in the future timelines continually slip back to menace the mutants of today. A new generation of mutant hunting killing machines seems to be slowly emerging, but only time will tell if the Sentinels will rise again.