Created by Bolivar Trask, the Sentinels' sole purpose was to protect humanity from mutants. This immediately put the mutant-hunting robots at odds with the X-Men. In the many years since the Sentinels' inception, they have proven to be a difficult group of enemies for the X-Men to take on.

There is still much mystery behind this advanced robot. Although they keep getting defeated and destroyed by the X-Men, it seems that more and more keep popping up. Here are the top ten secrets about the Sentinels that no one is supposed to know.

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10 10. Self Aware

The artificial intelligence within the Sentinels allows them to reason and develop a sort of limited consciousness. In the comics we see this problem manifest itself several times, leading to quite a few dire consequences.

When Trask first activated the Sentinels, he had them programmed to protect humanity from the mutant threat. Using their own reasoning, the Sentinels quickly determined that the best way to protect humanity was to rule over it. With their increasingly complex artificial intelligence, Sentinels have become harder and harder to control over the years. You never know exactly what they're thinking.

9 9. X-Sentinels

For a time, it seemed as though the Sentinel program was dead and never coming back. This happened to not be the case, as the Sentinel program was soon brought back stronger than ever.

After the US government initiated Project Armageddon, Dr. Steven Lang developed the Mark III Sentinels. Some of these Sentinels became known as X-Sentinels. This was because they bared the same resemblance and copied some of the powers of the X-Men.

8 8. Project Wideawake

In response to an assassination attempt by the mutant Mystique, the United States President gave the go-ahead on Project Wideawake. Project Wideawake secretly began developing a series of powerful anti-mutant weapons to help protect the American people.

After developing many weapons and gathering several anti-mutant super-teams, the Project brought on board the X-Men villain Sebastian Shaw. Shaw used his defense contracting company, Shaw Industries, to develop and utilize several new, upgraded Sentinels.

7 7. The Tri-Sentinel

When the Asgardian trickster Loki got his hands on three Sentinels of his own, comic readers knew the Marvel universe was in for some trouble. Using his arcane magic, Loki merged the three Sentinels, creating a larger, stronger Tri-Sentinel.

This Tri-Sentinel was then sent out to attack a nuclear power plant, which would have killed thousands of people. Fortunately enough, Spider-Man was able to stop the robot, using his new, temporary Captain Universe powers.

6 6. Bastion

Bastion X-Men Joe Madueria

When a mysterious mystical force merged the Sentinel Nimrod and a Master Mold, Bastion was born. Although both Nimrod and the Master Mold are completely robotic Sentinels, Bastion appears to be somewhat human.

Bastion then set out to find his own purpose, eventually becoming the leader of the Sentinels. This X-Men villain is seriously powerful and has created many dangerous new versions of Sentinels.

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5 5. Prime Sentinels

During Operation: Zero Tolerance, Bastion transformed a large number of humans into Human-Sentinel cyborgs that were forced to do his bidding. This new batch of robots became known as the

Prime Sentinels.

These Prime Sentinels were essentially sleeper agents. Not even they knew that they were cyborgs. Once a mutant gets within a close enough proximity, the Prime Sentinels directives would activate, forcing them to kill the mutant. Of all the humans who Bastion had transformed, there was one who stood out among the rest. Her name was Karima Shapandar, later known as Omega Sentinel.

4 4. Omega Sentinel

Omega Sentinel

A police officer from India, Karima Shapandar and her lover were both captured by Bastion. He tried to turn both into Prime Sentinels but was only successful at turning Shapandar because her lover was actually a mutant. After escaping, Karima painfully held of her Sentinel programming and told her boyfriend to run. Otherwise, she would have killed him.

Sometime later, Karima found herself on the island of Genosha where she met Professor X and Magneto. The two mutant leaders used their combined powers to disable Karima's programming and give her free will back. Now in control of her deadly cybernetic body, Karima decided to become a hero known as Omega Sentinel. She even joined the X-Men for a time.

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3 3. Nimrod

Created in an alternate future, Nimrod was designed as an indestructible descendant of the Sentinels. Named after the Nimrod from the bible who was known for his hunting abilities, Nimrod's sole purpose was to find and exterminate mutants.

When the mutant Rachel Summers traveled back in time, Nimrod followed her bringing him into the mainstream Marvel universe. Since coming to this new time, Nimrod has made it his mission to defeat the X-Men and successfully exterminate the mutant threat.

2 2. Dr. Steven Lang's Secret Agenda

Following the death of Bolivar Trask, the Sentinel program was passed down to his son Lawrence. A while later, Lawrence died as well, leaving the robots under the charge of Dr. Stephen Lang on behalf of the United States government. Little did the government know, Lang had his own agenda.

Secretly, Lang was an anti-mutant bigot hellbent on abetting their extinction. A member of the villainous Hellfire Club, Lang used both the government and Hellfire Club resources to create an army of Sentinels ready to exterminate the mutant threat.

1 1. The Master Molds

Master-Mold

Towards the end of the X-Men's first conflict with the Sentinels, they met and fought the deadly Master Mold. A giant Sentinel, the Master Mold is designed to create entire armies of Sentinels to combat the mutant population. They can produce a seemingly endless supply of Sentinel foot soldiers.

Although they defeated this first Master Mold, the Sentinels had one secret the X-Men weren't privy to. There were actually dozens, if not more, Master Molds created and sent to various agencies and locations all over the globe. There are most likely still many Master Molds hidden in the world, secretly producing the X-Men's end.

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