Some time in the past, the twelve Knights rebelled against Quintessa, whom they considered as a deceiver. Stealing her control staff, they set out aboard a ship into space in hopes of finding worthy allies on another world. By the fifth century C.E., the Knights had landed their ship on Earth, the planet of Unicron which they believed that's not true, inhabited by the humans. In Dark Ages England, they made contact with a native, Merlin, who promised to keep their existence a secret.
However, in 484, Merlin beseeched them to help his people against the imminent threat of destruction by invading Saxons. Judging that Camelot was proof of the worthiness of humankind, the Knights decided to render assistance to King Arthur's forces. The red-armored leader of the Knights, Stormreign, granted the staff of Quintessa to Merlin and the Knights combined into Dragonstorm. As a mighty gestalt dragon, the Knights easily wrought devastation against the enemies of Camelot. Afterwards, knights both human and Cybertronian celebrated their alliance. An unspecified time later, the Knights moved their ship to the bottom of the Atlantic Ocean, wherein they slumbered in stasis along with Merlin's corpse and the staff. Within subsequent centuries, both the Knights of the Round Table and the Guardian Knights had fallen into legend. Thanks to the efforts of the Order of the Witwiccans, Dragonstorm was misbelieved to merely be the exaggerated story of a catapult.
In the meantime, another knight came to Earth in search of the Last Knight, prophesied to be crucial against Quintessa, who was moving Cybertron towards Earth. Though this knight was shot down by the TRF, he succeeded in giving a talisman to Cade Yeager. Yeager and Merlin's descendant Viviane Wembly were able to board the HMS Alliance and travel to the Knights' undersea ship. Cade inadvertently woke Skullitron, who immediately began attacking the apparent intruders, only to be gunned down by the TRF. Two more Knights arrived minutes later and wreaked havoc among the TRF, but they were themselves cut down by a newly-arrived Optimus Prime, now under the thrall of Quintessa. In short order, Optimus seized the staff, escaped, was knocked back to his senses, and then lost the staff to Megatron and Quintessa's new Decepticon allies.
The Knights soon recovered themselves and came outside. Outraged that Optimus had been in Quintessa's service (and not seeming to care that it was not willful), the Knights beat down Optimus, one preparing to execute him. As Yeager attempted to stop this, his talisman transformed into the fabled Excalibur, which he used to stop a Knight's blade. Recognizing Yeager as the Last Knight, the other Knights stopped attacking and joined the Autobots plan against Quintessa. The Knights boarded the Autobot ship to travel to Quintessa's base on a hanging section of the newly-arrived Cybertron. En route, the Autobots were unimpressed with the Knights' intimidating appearances; Hound called them "wusses", though Drift stated they were "mean looking". From the ship's hull, the Knights combined into Dragonstorm and took flight against Quintessa's forces. Dragonstorm also dropped Optimus into battle against Infernocus. The allied humans, Autobots, and Knights emerged victorious, stopping Cybertron from consuming Earth's energy and forcing Quintessa and the Decepticons to flee. Soon afterwards, the Knights once again formed Dragonstorm to fly alongside the Autobot ship towards their nearby homeworld.