Hi @circus20204 ! These comments give me life! Here is the answer and a little ficlet to accompany it.

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CX-1 wasn’t like the Mirror Squad. He had no augmentations, no DNA manipulation. 

He used to be a Clone Trooper, with a squad and a clear path ahead of him: Fight and Die for the Republic.

CT-3031 was just another white droplet in the plastoid sea of the Grand Army of the Republic.

That’s why he was perfect for the CX program. If Hemlock could turn a run-of-the-mill clone trooper into the perfect killing machine and a true believer of the Empire on top of that? It meant Hemlock could have all the funding he wanted for his division.

CX-1 wasn’t the first to undergo the experiment. He was, however, the first to survive.

The success of CX-1, meant the success for Project Broken Mirror, which allowed Hemlock to bring the once rebellious Defective Batch to heel. And so…the Mirror Squad became Hemlock's thralls. 

When not doing his bidding, Hemlock always kept CX-1 locked in a pod like a prized art piece in his own private laboratory. 

CX-1 wouldn't remember this but once upon a time, his name was Avalanche and incidentally...he kriffing hated tight spaces.

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Pick of the Litter

“Tell me, Commander,” Hemlock purred coolly, as he stood alongside Commander Cody, observing the clone army march by in celebration of the First Days of the Empire. “Who would you consider to be the most average of your troopers?”

“Average, sir?” Cody asked. 

“Undeniably average. No record blemishes or accolades. No reason to stand out. Tried and true and middle of the road."

"Well, let me think..." Cody scanned the army below as if any one of them would jog his memory. Perhaps they would. Hemlock had no doubt in Commander Cody's keeness for details. What a magnificent specimen he may be one day.

"May I ask why, sir?"

"I need…” Hemlock drew in a deep breath, as if inhaling the intoxicating aroma of his own ambition in the air. "...a clean slate.”

“Off the top of my head, I’d say Avalanche is probably your man.”

“Avalanche,” Hemlock frowned slightly. “An exciting name for an average clone.”

Cody shook his head. “Not exactly. A sack of flour fell on his head in the mess hall when he was a cadet. The name stuck. A lot of trooper names are borne like that.”

“I see…” Hemlock massaged his gloved hand, working futilely against its atrophy.

“Sir, may I ask what your plans are with him?”

Hemlock could tell by the Commander's tone that he was concerned. These clones were growing far more emotional and less obedient by the minute. Tarkin was right to pursue conscripts at this stage.

“My plans? All my plans are aimed to ensure peace and security is maintained in our galaxy.” Hemlock narrowed his icy blue eyes. “Is that not your plan as well, Commander?”

“Sir, yes, sir,” Cody stiffened, but his eyes remained hard and unblinking.

Hemlock smiled at Commander Cody, already imagining ways of applying the proper pressure to bend this strong-willed commander to his will. But no...no not, yet...patience....

Okay, since there’s been a lot of discussion around CX-1 from the season 3 trailer, I want to give us all a little refresher on how the original Clone X was revealed to us in season 2, the similarities they’re showing between him and CX-1, and what purpose they might be serving in the story.

This is not meant to engage discussion on whether the helmeted CX paratrooper in the trailer is Tech. We don’t know yet if the helmeted clone and the helmetless, deep-voiced clone are the same, or two different CX troopers. All we know is that the helmetless one who has spoken lines in the trailer, is named CX-1 in the subtitles.

Season 2:

We are introduced to the assassin clone known as Clone X in the beginning of episode 7, The Clone Conspiracy, as he is tracking and firing on two clones who were there during the destruction of Kamino and had been contemplating revealing Rampart’s deceptions. Many people thought this could be Crosshair, but based on his less skillful shooting ability and the faint glimpses of his unusual armor, I didn’t think it was.

We then see him fully via a holocall to Rampart, where the garble of his helmet (again, very different than a regular helmet modulator) conceals his identity as he is told to hunt down Slip and Chuchi. Later he finds and kills Slip and several of Chuchi’s guards, attempting to kill her during a prolonged chase (for an assassin, his shots are noticeably not as precise as Crosshair’s or many bounty hunters are), and Captain Rex as well, who appears out of the fog and saves her. He had been in the area to help Slip get to safety, and ended up stunning CX and bringing him into the Martez sisters’ garage for interrogation.

This of course ends up being the most fascinating aspect of this clone’s arc. Rex undoes his helmet and both he and Chuchi are shocked to find a familiar clone face hidden beneath it. Chuchi wonders why a trooper would be doing this and Rex feels like they’re not a trooper at all, but that he doesn’t know what they are. Once CX wakes up from being stunned, Rex tries to get him to talk and find out who sent him and what his mission is, but he stays stubbornly silent.

Once Rex offers to release him if he’ll just talk, he begrudgingly spits out “no you won’t, Captain Rex,” showing that he knows who Rex is and that he doesn’t seem to be surprised that he is alive, even though Rex’s official records state he died. CX then hauntingly says “You’re fighting the wrong battle, brother—you’re limited.” When Rex asks him what that makes him, he responds even more chillingly “a believer” before biting down on a suicide capsule.

None of this terminology or behavior is normal for clones or imperial troops that we have ever seen before. He appears to have been brainwashed in some manner that is very different than any enhancements or conditioning that Crosshair went through or that other imperial clones such as Cody seem to demonstrate. He has become a tool solely at the disposal of Rampart and whoever else in the Empire is putting him to use.

This seems to be confirmed in the next episode, where in examining his body, Rex had determined that all of his original CT identifications implanted by the Kaminoans had been wiped. Perhaps his mind had been too. CX is said to have been born in the first wave of troopers in 32 BBY, which would explain how he knows Rex, and that he is not a new clone creation but an original CT trooper who has been “repurposed” for this program.

Note that in this season we don’t get an answer on who is actually overseeing his training or brainwashing or anything else related to him. He seemed to be taking orders only from Rampart, but with Rampart off the stage after these episodes, it seemed likely that this CX program was bigger than just Rampart’s department or efforts. Sure enough, season 3 seems to be confirming that.

Season 3 (TRAILER SPOILERS AHEAD):

We see at least one, perhaps two new CX troopers in the season 3 trailer. A clone assassin named CX-1 has voiceover that precedes the reveals of an imperial commando, the bounty hunters we’ll see this season, as well as Nala Se with the words “They are coming…” and then it switches to the visual of his face as he finishes “for ALL of you.” And the visuals then show a quick sequence of the majority of our heroes—Wolffe, Hunter, Rex, Echo, Fireball, and Omega, and Wrecker—the “all of you”. This speaking clone has the same generic face and haircut that CX showed in season 2, as well as the same deeper register but with a honeyed smoothness to his voice that is very different from the rest of the regs or the gravelly pitches of the Batch boys. All in all, he seems like a copy (I know I know) of CX in season 2.

In both instances, it appears the X troopers dialogue comes when they are being interrogated by someone they were trying to hunt down. Beyond that, we still don’t know much about their origin and purpose in the broader shift away from CT to TK troopers mingled with Palpatine’s cloning efforts.

Also, I just can’t stop thinking about both troopers’ voices. Why are they so much deeper? And CX-1’s smoothness compared to most of the clones makes me think that the X-number troopers are clones of CX and much younger? Their voices haven’t had as much usage as the clones who have been through the entire war? I don’t know. It’s intriguing though.

I am fascinated to see exactly how much more expansive of a role the X troopers and potentially their program are going to serve in this season. Perhaps they will remain mysterious and simply be yet another way that Palpatine and Hemlock have twisted the clones’ existence to suit their purpose, and to act as a harbinger for what’s to come. Or perhaps they will be a pivotal hinge of this season in more depth this time. We shall see.