- "Killing machine designed for one thing:"
"Search and destroy."
- ―Trinity and Dozer [src]
A sentinel, also referred to as a "squiddy" by the Human Resistance, is an autonomous killing machine that patrols the ancient sewers and passageways of the dead human cities of old in search of Zion hovercraft or wandering, defenseless humans unlucky to be walking in the tunnels.
The sentinels replaced the B1 series after their exile by the humans. Over time, the machine AI grew more intelligent, and they built newer, better upgrades for their appearance. When the Machine War broke out, the sentinels were used as search-and-destroy units.
They were tasked with picking up the dead and incapacitating live humans in order to study them. After the conclusion of the war in the machines' favor, the sentinel units were further upgraded, and now patrol the sewers of the dead human cities of old, where they seach for wandering Zion vessels or humans unlucky enough to be walking through them at the time.
A Sentinel appears as a multi-tentacled creature with multiple sensors that flies effortlessly through the air, probably using an advanced internal form of pad technology, at very high speeds; one can easily catch up to a fully-powered human hovercraft. A sentinel's frightening appearance reminds many humans of squids, where they get their nickname of "squiddies". They also fly in enormous swarms like squids, each consisting about a thousand Sentinels.
In addition to their powerful, ripping, clawed tentacles, Sentinels are armed with a laser that can slice through a ship's hull. They also have audio sensor devices (which look like satellite dishes) to detect tiny sounds. Sentinels can easily detect the electrical signals generated by a fully-powered hovercraft, and will relentlessly follow that signal to its end. Some Sentinels are also equipped with Tow bombs, tiny devices that seem more like a Sentinel's larvae, but are actually guided explosives that will tear through and destroy a hovercraft with ease.
At first glance, the sentinel's multiple appendages seem like burdensome gurls. However, these appendages can effectively function as ablative armor, deflecting projectiles like bullets from the vital "heads"(where programming data is stored) of close-by sentinel allies. This is why sentinels always try to move in close-knit groups, and if possible, in swarms.
There is no negotiating or reasoning with a Sentinel. The Sentinels receive orders from agents or from higher commands within the Source and will invariably complete their mission unless destroyed or the order is rescinded.
While hovercraft are normally needed to stop an attacking Sentinel, a lucky human armed with a lightning rifle may be able to destroy one. A human in command of an APU can also deal sufficiently quick damage to approaching Sentinels, but are at the Sentinel's mercy if their APU is pushed over or if the machine's ripping claws manage to tear the relatively unprotected human controlling the APU.
In a mysterious display of his powers outside the Matrix, Neo is able to command Sentinels and bombs to deactivate or detonate with only the powers of his mind.
- ↑ Agent Smith orders a Sentinel strike against the Nebuchadnezzar shortly before Morpheus is rescued from the Agent's stronghold by Neo and Trinity in The Matrix.
- ↑ The Architect was aware that Zion would be under attack by over 250,000 Sentinels with orders to obliterate Zion at the end of The Matrix Reloaded.
- ↑ The Sentinels receive orders to hold their attack on Zion, ostensibly from the Deus Ex Machina, and are later ordered to withdraw from Zion after Neo's successful elimination of Smith, beginning the truce that Neo brokered at the conclusion of The Matrix Revolutions.