The first arc of the seventh and final season of The Clone Wars focused heavily on Rex and the Bad Batch, going on a mission in search of Echo.
In the second episode, “A Distant Echo,” they find what they’re looking for: Echo is alive, though in a badly damaged state. Mention is made of something that happened at the Citadel, but what’s that all about?
If you’re just now getting into The Clone Wars with this season, or if you simply forget what happened in the previous seasons with Echo, allow me to refresh your memory of what led us to this moment!
Echo’s first appearance in the show is in the fifth episode of the first season, “Rookies.” But canonically, we see in season three that he was a member of Domino Squad during his training on Kamino. This squad had difficulty working together as a team, which put them in danger of failing the tests. Eventually they pulled it together and wound up with one of the most impressive runs in the course. This success led to them being stationed on the Rishi moon, a remote communications outpost in the Outer Rim that was key to protecting Kamino. During Domino Squad’s watch, a Separatist strike force secretly infiltrated the post, forcing the clones to rally. Teaming up with Commander Cody and Captain Rex upon their arrival for a surprise inspection, Domino Squad successfully foiled the Separatist plan by destroying the outpost, thus stopping the all-clear signal from being transmitted.
Echo and Fives were the only members of Domino Squad to survive this encounter, however, and they were made members of the 501st, to serve under Commander Rex and General Anakin Skywalker. Before long they were back on Kamino, fighting to defend the planet from a massive Separatist attack led by General Grievous and Asajj Ventress. Jedi Generals Obi-Wan Kenobi, Shaak Ti, and Anakin Skywalker commanded the Republic efforts, while the clones teamed up with 99 to repel droid forces and protect their home. 99 (who is the namesake for the Bad Batch, “Clone Force 99”) lost his life in the effort, but Kamino was saved.
Later, Echo was part of a strike team (again led by Kenobi and Skywalker) to infiltrate a place known as the Citadel, a menacing Separatist prison on the planet Lola Sayu that was known for being able to imprison Jedi. Jedi Master Even Piell had been captured and imprisoned there, and this strike team was given the mission of rescuing him. They snuck onto the planet by being frozen in carbonite, and managed to infiltrate the prison and rescue Piell and his captain, Wilhuff Tarkin. In an attempt to escape, the Republic forces tried to fight their way onto a shuttle to escape.
Echo noticed a Separatist droid preparing to fire on the shuttle and took matters into his own hands, trying to stop the droid from firing. He was too late, though, and the droid fired a shot that caused the shuttle to blow up. Echo, having tried to protect the shuttle, was caught in the explosion, presumably dying. The Republic would eventually escape, though lost Echo and Piell in the process.
But that’s where this arc comes into play. The Republic had long presumed Echo to have died in the explosion at the Citadel, but then Rex grew suspicious during the Battle of Anaxes in the late stages of the war. He realized that the Separatists knew his playbook, and that he and Echo had developed it… so in a mission to discover more, Rex’s suspicions were confirmed: a live signal was transmitting. Echo was alive.
So Rex accompanied Skywalker and the Bad Batch to Skako Minor, tracing Echo’s signal there. They fought their way into Wat Tambor’s Techno Union facility, eventually finding Echo. He was in bad shape, having been kept in stasis for so long, and had many cybernetic parts attached to him. He was hooked up to the Separatist machines that basically manipulated him and used him for information. As Rex and Tech began bringing Echo out of stasis, he picked up where his previous memories had left off, assuming he was at the Citadel and that Rex had come back for him.
After successfully rescuing Echo, the Republic later utilized his skills on a mission to take control of Anaxes. Echo used the Separatists’ plan against them, sending them battle plans that lured them into a trap. For his actions in aiding the Republic victory on Anaxes he was lauded and praised, but he headed off to join Clone Force 99 as the episode ended.