The Sentinels are mutant-hunting robots, specifically programmed to target the mutant X-gene. They are used by Sentinel Services to hunt and apprehend mutants that are too dangerous for agents to approach.
The exact history of the Sentinels is unknown. However, they were likely developed sometime after the creation of Sentinel Services.
In eXposed, Sentinel Services surrounded the Strucker family and several mutants from the Mutant Underground (Eclipse, Thunderbird, and Blink) in an abandoned warehouse facility, and ordered them to the ground. When the fugitives refused to comply, they deployed the Sentinels to hunt them down throughout the warehouse. Despite their best efforts, they failed to apprehend the subjects due to Blink's ability to create portals, which allowed them to escape. The robots were able to withstand Thunderbird's strength, Eclipse's heat blasts, and Lauren's force fields. Andy was the only mutant powerful enough to defeat them by tearing the Sentinels apart with his ability.
In outfoX, the Sentinels were unleashed against Dreamer, Blink, Andy, Lauren when they broke into the power station. Andy attempted to destroy it as he did at the warehouse but found that the robot was stronger and more resilient than the last time they'd encountered them, showing that the Sentinels had been modified. One of its legs was disabled but it detached and the robot moved somewhat normally as it kept up the pursuit. While the rest of them did manage to get away, the Sentinel did manage to capture Blink after tackling her to the ground.
They are small spider-like robots with a rotating red eye in the center. They are extremely durable and can withstand intense physical assaults and intense heat, capable of quickly adapting to damage to continue functioning. They capture mutants by latching onto them with immense grip, even Thunderbird could not break free from a sentinel until Eclipse assisted with an intense heat blast and even then the sentinel continued to function and hunt them. Thus far only Andy has been shown to have powers strong enough to destroy them. With their spider-like design, they can crawl and maneuver on walls and ceilings.
- The Sentinels made their first appearance in the 1965 comic series titled "Uncanny X-Men #14".
- They also appeared in the X-Men cinematic universe, debuting in X-Men: Days of Future Past as giant humanoid robots.