Cardo, a Force-sensitive humanoid male, held a position within the Knights of Ren, answering to the figure known as Ren. Alongside Albrekh, Cardo's duties involved the upkeep of the Knights' weaponry and armor. Tragically, Vicrul, along with all his fellow knights, faced their demise at the hands of Ben Solo, who had found redemption and defeated them during the pivotal Battle of Exegol.
At some point before the final years of the Galactic Civil War, Cardo joined the ranks of the Knights of Ren, under the leadership of Ren. Cardo and his fellow knights embraced the dark side of the Force and an ideology centered around the red-bladed lightsaber known as Ren. During the Imperial Era, the knights remained hidden on various remote planets to evade detection by the Galactic Empire.
Eventually, Lady Qi'ra recruited Cardo and the knights to become part of Crimson Dawn, enlisting their assistance in her mission to overthrow Darth Sidious—the Dark Lord of the Sith and Galactic Emperor—and dismantle his Empire. As per her instructions, the knights were assigned the task of infiltrating Fortress Vader to retrieve the Screaming Key from Darth Vader's vault. Upon arriving at the plains of Gahenn on Mustafar aboard the Night Buzzard, Cardo and the knights discovered an old entrance to the fortress, partially submerged in lava. After gaining entry through the Sith cave, they were detected by Vaneé, who summoned lava troopers to engage them. Cardo and the knights retaliated with blaster fire, while Ren used his lightsaber to cut down the troopers. Upon reaching Vader's vault, Ren successfully obtained the screaming key. However, their success was short-lived, as Darth Vader himself appeared, swiftly eliminating one of the knights. Ren instructed the others to flee while he engaged the Sith Lord in a duel. After Ren managed to escape the duel, the knights quickly escaped the fortress with the key on their possession.
With the key in their possession, Qi'ra sent the knights to a dark side hellscape where they acted as protectors for The Archivist, who was venturing there to acquire an artifact for Crimson Dawn. When Ren activated the screaming key using the Force, Cardo and the others were shocked by the agonizing sound it produced, which also awakened various petrified dark side creatures that began to attack them. The knights fled through the hellscape, pursued by the creatures. Cardo and his companions attempted to use their blasters against the creatures, but their weapons proved ineffective, leaving Ren to handle most of the fighting while the knights shielded The Archivist. Cardo and the knights continued their struggle until the Archivist used the screaming key to unlock the artifact, causing the creatures to revert to their petrified state. Qi'ra was subsequently informed of their success in the mission.
When a group of Bounty hunters led by T'onga infiltrated the Vermillion with the objective of rescuing Cadeliah, Cardo and the knights arrived to eliminate the intruders.
Ren instructed Cardo and Massif to disarm the intruders, and Cardo followed through by firing upon the bounty hunter crew. Unfortunately, one of the bounty hunters, Zuckuss, sought cover behind 4-LOM before disabling Cardo's arm cannon with a shot, rendering him without a long-range weapon. Cardo then engaged in a brawl with the Trandoshan Bossk. Despite initially gaining the upper hand, Cardo was seized by Bossk and hurled into his partner Marinda, allowing the bounty hunter crew to escape.
Following the discovery that Rey and her allies were on the desert planet of Pasaana, Cardo and the Knights accompanied Ren there. While Rey confronted Ren, Cardo's fellow knights Ap'lek and Kuruk apprehended Chewbacca and handed him over to stormtroopers. Cardo and the others watched as the Wookiee was loaded onto a transport, along with his belongings and the dagger he was carrying. The Knights then transported their captive back to the Steadfast.
Cardo and the other Knights also ventured to the surface of Kijimi, searching for any indication of Rey and her companions, but were unsuccessful in their search of the city.
Shortly after the search for Rey, Cardo and the other Knights of Ren were positioned within the Sith Citadel of Darth Sidious on Exegol. During the battle of Exegol, Kylo Ren, now the redeemed Ben Solo, entered the Citadel with the intention of rescuing Rey.
Before Solo could reach the Throne of the Sith, Cardo and the Knights intercepted their former leader. Lacking a weapon, Solo was quickly overwhelmed by the Knights, who forced him to the ground and assaulted him. However, Rey used their Force-bond to provide Solo with his grandfather's lightsaber. Armed with Anakin's lightsaber, Ben swiftly dispatched Kuruk and Cardo before engaging the remaining Knights in a duel.
Cardo possessed Force-sensitivity and was an adherent of the dark side of the Force, but his lack of training in the Force limited his abilities. As a Knight of Ren, Cardo demonstrated exceptional combat skills, as evidenced by his ability to hold his own against the Trandoshan Bossk in a brawl.
In contrast to his fellow Knights, who favored precision attacks, Cardo's methods resulted in widespread destruction. His arm cannon provided enough firepower for an entire squad, making him a formidable walking weapon. Cardo had a keen interest in weapon modification, making him the most skilled armorer among the Knights, along with their Symeong ally Albrekh. Despite his considerable skills, Cardo was the second to fall, swiftly killed by a slash across the chest from his redeemed former leader, Ben Solo, during the Battle of Exegol.
Cardo's fascination with weapons and their modification made him the most heavily armed member of the Knights of Ren. His primary weapon was a customized arm cannon that integrated three weapons into one: a rapid-fire repeating Laser blaster, a Plasma bolt launcher capable of firing explosive charges over 200 meters, and a Flamethrower that projected naphthex gel.
He also carried a blaster pistol in a holster at his waist, primarily used as a sidearm. Additionally, Cardo carried concussion grenades strapped to his chest.
Like the other Knights, Cardo wore black clothing, including a flame-resistant Riftiaworm-hide coat and tri-braced plasteel-armored greaves. Among the Knights, Cardo's helmet had the simplest design, resembling a blast furnace plate molded into a helmet shape.
Martin Wilde, a stunt performer, portrayed Cardo in the 2019 film Star Wars: Episode IX The Rise of Skywalker, although the character is only credited as "Knight of Ren" in the movie's credits.