Sentinels are robots designed and developed by anti-mutant bigot Bolivar Trask and his company of Trask Industries to hunt down mutants. They first made their live action debut in X-Men: Days of Future Past.
X-Men: Days of Future Past
By the year 2023 in a dystopian future, the worst of the worst rule the world, the mutants are either hunted down or killed. They also go after the humans that have sided with mutants and harbor the X-gene in their body for future offspring. The only resistance against them however were the Free Mutants who consisted of what remained of the Brotherhood of Mutants and X-Men.
This group was able to evade Sentinels due to the fact that Shadowcat sent Bishop's mind into the past. This would assist them in avoiding the places they would most likely ambush. It was too late for some of the mutants though as they were cornered within a monastery in China. Kitty sent Wolverine's mind back in time the same way in order to stop all this from ever happening, which meant stopping Mystique from killing Trask.
Once back in 1973, Wolverine found Professor X and Beast, explaining to them the situation. After saving Trask however, they inadvertently cause the existence of mutants to be revealed to mankind. It's then that Trask convinces President Nixon to approved of his Sentinel program. Despite assuring the president that the robots were not composed of metal, Magneto managed to sneak metal parts in each of the Sentinels which were unveiled at Washington D.C. Once unveiled, Magneto then uses the Sentinels to scare the audience away before he dropped an entire stadium around the white house. Wolverine and Beast attempted to stop him only to be confronted by a Sentinel. Magneto confronted Wolverine, stabbing him with rebar and sending him flying. The Sentinel went after Beast, thankfully though Hank injected himself with a specially designed serum, changing him back to normal.
This caused the Sentinel to only target Magneto and Nixon who was really Mystique in disguise. Mystique shot Magneto in the neck, stunning him and shutting down the Sentinels, but before taking out Trask is talked out of it by Charles Xavier. Mystique doesn't kill Trask, the Sentinel program is shutdown, Trask is arrested for disclosing military secrets and the timeline Wolverine once knew has been averted.
As machines, Sentinels have been designed solely for combat.
- Superhuman Strength: A power that a Sentinel naturally has is the ability to lift tons over their head with great ease and fight with the same strength. Two Mark 10 Sentinels were strong enough to tare Colossus in half. One Sentinel could take down Colossus with one hit in head, stunning him on few second on ground. Sentinel was also able to throw him away across room. Sentinel grabbed Colossus with one hand and held him firmly by the fist, immobilizing him. Sentinel alone proved to be equal, if not more powerful than Colossus.
- Superhuman Endurance: Sentinels are built out of a space age polymer, which is very powerful and durable, making Sentinel very resistant to most of weapons and mutant powers. It is seen that only Bishop's energy weapons and powerful destruction explosion of Sentinel space ship can actually damage or destroy them (Sentinel X at least). Other weapons and powers can only slow them down. Due to that, if they upgrade their armour with some mutant power, they can get additional armour (Iceman, Sunspot) or get near indestructibility (diamond, rock or Colossus' metal form).
- Power Mimicry: Although earlier models didn't possess such an ability, the Mark 10 Sentinel evolved to the point where they can mimic the powers of virtually any mutant they came across.
Not just that they can replicate a mutant's powers, those replicated powers are more powerful than powers of original mutants. For example, Sentinel in ice form could successfully move towards Sunspot without trouble, and shut down/freezing with one hand. Sentinel in heat/lava/sunspot form could successfully break Iceman's ice, holding him for neck and crushing his head off. In this form he could melt treasury's heavy door in seconds. Sentinel in metal form taken from Colossus could kill Colossus himself in just two hits in head. After first hit, Sentinel ripped out Colossus's hand. This is because all mutants powers are upgrade to human body, while Sentinel's copied powers are upgrade to this very durable material which Sentinels are build from, so they can create more powerful abilities, making Sentinels invulnerable in some cases.
Sentinel are also seen to morph into rock form (probably mimic Darwin's rock form), gaining extremely durability, more weigh and immunity to sunspot's heat energy weapon. In such form, while he misses sunspot with hands, Sentinel hit ground, making it explode, demonstrating very increased strength.
Another Sentinel under Sunspot's attack is seen to morph into diamond form, mimicking Emma Frost's diamond form, upgrading to his own powerful armor, making him immune to. sunspot's energy heats too. In this form he could create diamond spike which was cut off sunspot's hand.
- Flight: Sentinels were designed with thrusters within their foot allowing them to defy gravity. By the year 2023, the mark 10s were designed with hover devices enabling them to fly on their own without jet thrusters.
- Athletics / Agility: Sentinels are seen to be very agile, they could do somersault forward and backward in air and were able to jump at higher distance. They are seen crawling over walls in Chinese monastery (one was climbing up, and few were climbing down)
- Shape Altering/Weaponizing: Thanks to Mystique's shape altering power, Sentinels are also seen to be able to alter their forms to fit variety of purposes:
They could become smaller/larger, as explained by developers. This also could be seen in first scene when transporters began to open doors and launching down Sentinels one by one. Those Sentinels did not have hands and legs, perhaps because so more Sentinels could fit into transports. They also could extend their arms into long and extremely sharp spikes capable of breaking though concrete walls and stabbing/cutting mutants. (Sentinel cut off Sunspot's hand, another Sentinel were impaling and killing Sunspot in his lava form with long claws coming out of each finger). Before first battle against X men, Sentinels were drilling though concrete walls with powerful drills. It took few second until they break though concrete, then almost immediately drills converted back into hands.
- Immunity to certain weapons: As robots, Sentinels are immune to psychic attacks from Xavier and other telepathic mutants. They are built out of a space age polymer, making them immune to Magneto's control. They have X-Gene detector to detect mutants from very long distance, which means that shape changing mutants like Mystique cannot fool them disguising into humans.
Sentinels have evolved since their creation in the 70s and therefore have utilized a variety of different weapons along the way.
- Chain Guns: In their earliest form, Sentinels were armed with high powered chain guns that looked similar to that of the General Electric M61 Vulcan. They were located on their left arm.
- Head-Based Lasers: The Mark 10 Sentinels were designed to emit a high powered laser by only is emitted when the face of the robot opens like a flower.