FALL OF THE REPUBLIC
Also known as CT-1409, Echo was a member of Domino Squad on Kamino before graduating and joining the fight against the Separatists. He survived a Separatist attack on the Rishi Moon listening post, was decorated for bravery, and inducted into the 501st Legion. Echo and his fellow Domino, Fives, later helped defend Kamino against a Separatist invasion, and were promoted to ARC troopers after the Separatists retreated. The two also helped Anakin Skywalker and Obi-Wan Kenobi free prisoners from the forbidding Separatist prison known as the Citadel, a mission that cost Echo his life -- or so his friends believed.
Seemingly lost in battle at the Citadel, Echo met what may have been a fate worse than death: Separatist capture and experimentation. The clone was turned into a cyborg, able to communicate with computers and decode the Republic’s strategy algorithm.
While on a covert mission with the Bad Batch squad, captain Rex detected a signal -- a voice saying, “CT-1409” -- leading him to believe that Echo was still alive. Rex was determined to find his friend, and finally tracked him to a Techno Union base on Skako Minor. There, Rex and Bad Batch finally freed Echo from his living prison of wires and programming.
The trooper was disoriented but alive, and eventually regained his full consciousness -- along with the ability to understand Separatist transmissions. He played a key role in a major Republic attack on the Separatists at Anaxes, and was honored for his bravery.