Echo always knew he was one the rabble -- another clone in the lineup, interchangeable, replaceable, and so was everyone else around him. The Elders didn't exactly bother to keep the secret when it came to the Sectoids anymore; at this point, the Sectoids are basically just easy lab rats whenever the Elders find some interesting new DNA to fuck around with. Echo's pretty sure that at this point, any record of their original genome is either buried in the Elders' high-security archives or just got trashed some several-hundred years ago. At least the Mutons and the Vipers at least had the respect to still get lied to.
Not that the Elders didn't keep up some appearances with the Sectoids. After all, the ones who were special enough got to be Commanders-- not because of any inherent skill or natural talent, they all had exactly the same potential. Probably just because they were more willing to debase themselves than others to kiss the Elders' flat, wrinkly asses. Echo never had the patience to jump through those hoops, so on the lowest rung he stayed, a bitter little pill of a man.
Invading Earth was something to do, at least. Finally, he could take out his frustrations on a species weaker than he was (or at least, people who were unarmed and ignorant). After a lifetime of being another nobody in a sea of nobodies, it was nice-- until he got himself captured by a way-overeager freak of a woman who held him under the arms like a newly-bought pet. Worse, she didn't shut up and she didn't leave him the hell alone. He spent every day in captivity with her yapping about nothing whenever she found the time.
...
She apparently did think he was worth the attention, though. Enough that she actually tried to figure out what stuff he liked when she brought human entertainment junk over, and mentioned that he talked about him to other people, and even gave him a name. 'Echo' was kind of an insult, reminding him that he was just another bit of target practice, but whatever. She told a story about how humans originally explained the phenomena of sound repeating across space. Something about some lady who never got noticed.
Of course, Cargo didn't spend all her time annoying Echo, specifically. She had every other captive she brought in to ramble at. And besides, he also had to deal with Vahlen, the single most terrifying human Echo had met so far in the most understated way, and the bunch of assistants she had that ranged from boring to obnoxious to weird to condescending. (Apparently more than one human thought Sectoids were "cute".)
Echo snapped more than once, but he really went off on Cargo on a day when he'd just had enough of the bullshit the humans were subjecting him to. And given how much she talked, she'd given him plenty to target about her. Her obvious loneliness and desire for a friend, even/especially extraterrestrials-- those whom wouldn't have grown up with human standards of interaction and might even have low enough standards to like her. Her denseness and literal thinking. Her stupid line of logic, where she loved aliens, but was also perfectly happy to abduct or kill them based on whatever arbitrary thinking brought her to a decision. She didn't even argue with him.
The Berserker in one of the other cells did that for her, and Echo was smart enough to shut up when he heard something crack from her fists pounding against the walls. Hilariously, Cargo still tried to defend him, in that she assured the Berserker that his whole rant was perfectly fine for him to say. The Berserker did not agree.
Echo really regretted his outburst when, at one point, Cargo just stopped showing up entirely. Yeah, it was probably just because of the, uh, the baby situation with Echidna, but...
Well, Echo didn't really have a leg to stand on when it came to company. He was as miserable as that human was. And yeah, hard not to feel like a massive dick when she had been pretty much the only person not to treat him as just another Sectoid. Especially when she finally did come back (weirdly, showing up in Echidna's cell in the middle of the night) and she was suddenly a lot more hesitant about talking to him, just because she didn't want to bother him too much again.
When the Elders finally attacked the XCOM base, and Echidna broke out and warned everyone else that she'd kill anybody who didn't join her, Echo figured it was worth going along with her and Cargo. Considering how shit his life had been with the other aliens, Echo figured it couldn't hurt. ... And he owed Cargo an apology.
He was too much of a coward to give it, even once he got shot and there was nothing anyone could do to save him, and they'd actually tried. Echidna, and that one Thin Man desperate for the captive Elder's dick, and Cargo-- the latter two slowed his bleeding, Echidna had been the one to carry him out and ran back into the base to try and find supplies. Cargo held Echo while he died.
He really owed her an apology. He promised her a letter, instead, since she let him see a memory of her childhood where she tried to write one to aliens that she didn't even know at the time were real.
His epitaph read: One of Many, but One of a Kind.
The others still think about him sometimes; an echo of a chittering little jerk in the back of their minds.
