Soundwave glared after the children, frustrated that these tiny humans had managed to outwit him. However, surely Megatron would soon crush them and their Autobot allies, and return him from this dimension. After all, Megatron wouldn't forget his most loyal and competent servant, right? Once he had made sure that there was absolutely no way to open a groundbridge from this dimension to the preferred one, the Decepticon decided his best course of action was to watch the battle from the shadows.
Soundwave couldn't believe his optics. Megatron... lost? There was of course a chance he had survived, Megatron always made it through one way or another. And once that happened, he would open a bridge and rescue Soundwave. However, for the bridge to work, they'd have to open the groundbridge in the same coordinates that the bridges interfered with each other, otherwise, it may not work. How dare the Autobots act victorious in the meantime? They acted as if they won, as if they overtook the ship, as if Megatron had died. They could never overcome the Decepticons.
However, they played a convincing role, and soon were beginning to steer the ship.
Wait, steer the ship? Thought Starscream. If they moved too far, there was a chance Soundwave could never return!
Soundwave quickly attempted again to open a bridge to take him back, to no avail. He tried to communicate with Megatron, then with the remaining Decepticons, and then, out of desperation, anything nearby which may be able to hear him. Nothing. No bot or human showed a sign of receiving the message, or trying to respond. Soundwave could only watch in horror as the ship moved further and further from the original coordinates. Seeing no positive outcome of staying with the Autobots any longer, Soundwave ran to the nearest possible exit of the ship, jumped, and transformed. He flew to Earth in search of Megatron.
Weeks had passed, and still no sign of Megatron. Luckily for Soundwave, there were plenty of Energon deposits in the shadow world, and he had quickly amassed a large supply that could last him years. It was a bit lonely though, in this separate dimension. He could see and hear other life forms, but none could see, hear, or even touch him. He had worked solo many times before, but never to this degree. However, he wasn't about to let such a petty emotion as loneliness affect him. He marched on, in search of Megatron or any being that knew he was there.
Well, the Decepticon was right about one thing. The Energon deposits had lasted him a year, and there still seemed to be plenty more for the years to come. However, he had noted that he hungered less than he had previously. Perhaps it was an effect from this different dimension, or he lost his appetite from his lack of communication with anything. He never found Megatron, or any being that was aware of his presence. He hated to admit it, but he was lonely. Every now and then he thought he would hear Starscream or another Decepticon behind him, but when he turned, there was never anyone there. He began to fear for his sanity, but then again, what did it matter if he was sane or not? If anyone was coming for him, they would have found him by now. By the looks of it, he was to never make contact with any living creature ever again. Perhaps letting go of his sanity would help him, anyway. Allowing his imagination to run wild and even manifest itself could help him to feel a bit less lonely, and it would at the very least help cure his boredom.
Years continued to pass. Without having to share the shadow world's energon with anyone else, Soundwave had a seemingly endless supply. With this source of life energy, and with no other being to cause him harm, he had become nearly immortal. He watched as the human countries rose and fell, and as their leaders struggled for dominance. The humans only seemed to be aware of one solution for their struggles and rivalries: War. Soundwave could only watch from a distance as the humans used their bombs in wars scaling from small to worldwide. After a several seemingly short decades, the entire planet was ravaged by nuclear fallout. The Decepticon lost track of the years, but in what must have been about a century humanity was driven into hiding from the nuclear waste. A few survivors remained here and there, but life was scarce.
Without any company, the desolate bot sank further and further into his insanity. Having not worried about cosmetic appeal for quite some time due to lack of contact with others, he allowed damages and organic materials to contaminate him, to the point where he was so covered in moss and other filth he appeared green. Having only had humans for nearly a century as a guide on how to look and act, Soundwave wanted to fit in, even if they couldn't see him. Thus, he took a dead human's head which hadn't decomposed too terribly, skinned it, and wore the face as his own. It was disfigured from decomposition and Soundwave stretching it over his head, and the teeth had become half rotten, but it did the job well enough. He took some clothes from humans along with leftover fabrics and used them to make himself some clothing: A blue long sleeve shirt and black trousers. His natural stabilizing servos served well enough as shoes, so he left them alone. Finally, he grew desperately lonesome, so he took the last bit of his fabric and created a few finger puppets to be his companions. He gave each one of them a name, and because of his mental state, could hear them speaking to him. When talking to his new "friends", he became aware that he had forgotten his own name. No one had called him by it in so long that it had slipped his mind. In his mind, one puppet noted that his long fingers resembled leaves from a salad. The bot agreed, and derived from this comparison his new name. One that fit in his current state.
"Thank you for your wonderful input, Hubert Cumberdale," Said Salad Fingers, pondering his new identity, "Salad Fingers... It does suit me rather well."
Disclaimer: I do not own Transformers Prime or Salad Fingers. They belong to their respective owners. I do not own any characters mentioned. Don't sue me plox.