Guardian is an example of an Omega Class Battle Droid. Their bodies consists of two-foot-thick armour plating and a hydraulic musculature. They store enough energy to power a spaceship. Designed to be virtually unbeatable, they have two weaknesses: They are susceptible to strong magnetic fields which can interfere with their central data core, and they have a cerebral access point located on the neck that is large enough to fire a thin laser beam into, which can overload their cerebral circuits.
Marvel Comics UK continuity
During a Decepticon attack on the Ark, Optimus Prime attempted to activate the Ark’s computer, known as Auntie, to bring the defense systems back online. Unfortunately, Auntie had been damaged in the crash and become unstable. Unable to remember who was friend or foe, she used a magnetic field to subdue all the combatants—all, that is, except for Ravage and Windcharger whose magnetic powers allowed them to counter Auntie’s magnetic force. Working together to deactivate Auntie, they encountered the Guardian battle droid. Despite Guardian's power, Windcharger was able to disable him by using his own magnetic powers.
Guardian (it may or may not be the same one) was later encountered by Ratchet and the Dinobots as they returned to the Ark after it had been abandoned by the Decepticons. Before he left, Shockwave had reprogrammed Guardian to attack any Autobots who returned there. After receiving a sound beating that left Swoop injured, the Dinobots began hunting Guardian through the Ark. Managing to subdue him, they were about to destroy him when Ratchet and Wheeljack realised that the Decepticons had placed a thermonuclear bomb inside him that would destroy them all and Mount St. Hilary too.
They managed to prevent Grimlock from destroying Guardian by remotely activating the headless body of Optimus Prime and knocking Grimlock's gun away. Guardian managed to escape and, as per his programming by Shockwave, concluded that he could not defeat the Autobots and therefore he should locate them and detonate the bomb that he carried.
Guardian came hunting for the Autobots and engaged them in battle while the bomb counted down to detonation. Swoop was repaired just in time to fly Guardian far from the Ark before he could detonate. Sadly, he cut it far too fine, and was thought to be destroyed in the ensuing explosion.
- A Guardian droid would later fight and defeat Snarl in a dream in "Victory".
- Another type of battle droid with a similar body design and referred to as Guardian units were seen on Cybertron under the control of the Wreckers in "Under Fire". They may be a later model.
- A bulkier (but no less lethal) droid was seen aboard the Ark in "Yesterday's Heroes". It was described as a Mark V Guardian droid. This may also be a later model.