Echo formerly designated CT-1409 and known as the Hero of Anaxes, was a genetically defective human male clone trooper veteran Clone Corporal and former Advanced Recon Commando of the elite 501st Legion who served as a CT-99 clone commando of the elite Clone Force 99 in the Grand Army of the Republic during the Clone Wars. Originally identified as CT-21-0408, Echo was born on Kamino, a cadet of the Domino Squad, along with his friends Fives, Hevy, Cutup, and Droidbait, before he graduated from the clone training center. On his first assignment after graduating, Echo was tasked with guarding the Rishi Station moon base, where he, along with Clone Captain Rex, Clone Commander Cody, Fives, and Hevy, who sacrificed himself during the fight, aided in warning the Republic of an impending Separatist attack on Kamino. Echo was commended for his bravery and absorbed into the 501st Legion
After the attack on the Rishi Moon, Echo defended his homeworld from Separatist forces as they attacked Tipoca City, where they sought to destroy the Republic's cloning facilities. Once Republic forces successfully repelled the attack, Echo and Fives were both promoted to the elite rank of ARC trooper. Echo was later tasked with a mission to Lola Sayu, where he joined a group of Jedi and experienced clone troopers to retrieve coordinates to the Nexus Route from the Jedi Master Even Piell, who had been imprisoned on Lola Sayu's Citadel led by Commandant Osi Sobeck. After Piell and his surviving subordinates were rescued, the group headed for the landing field to escape on a shuttle. However, when Echo noticed a commando droid target their shuttle with a laser turret, he advanced to secure their ship, ultimately being blown up with the ship in a massive explosion that led his comrades to believe he was killed. Despite the loss of Echo and Piell's death later during the mission, it was ultimately a success
Unbeknownst to the Republic, Echo actually survived but was gravely injured as he was taken prisoner by Separatist forces, where he was sold to the foreman, Wat Tambor. Echo was kept alive by being turned into a cyborg, albeit at the cost of his consciousness. As a result of the Techno Union's experiments, Echo became a genetically defective clone. He became an unwitting pawn for the Separatists during their campaign on Anaxes, led by Admiral Trench. When Rex found traces of Echo's survival, he, accompanied by the elite Clone Force 99's Special Operations Brigade and Jedi General Anakin Skywalker, led a mission to rescue Echo on Skako Minor. They succeeded, and, in turn, Echo used his cybernetic capabilities to turn the tide against the Separatists on Anaxes, leading to the Republic's victory. After the mission, Corporal Echo decided to join Clone Force 99
