Tldr: Primus got fed up with cybertronians' bullshit, took their sparks and turned them into humans. Now bots are showing up at Earth's doorstep with flowers trying to win them back.
So imagine after eons of endless war the last of Primus' mercy has finally dried up, his creations has destroyed their homes, each other, him, nothing was scared any more.
They had taken his gift of life and desecrated it.
So if they were not going to value Primus' most precious gift he was going to take. it. back.
Primus would severe every spark from their mortal body and reincarnated them on a different world, far, far, away from their ungrateful hosts. Without a soul cybertronians were effectively immortal now, even if they were disintegrated down to the last atom their body would reform and rise again. This did not come without consequence of course, they slowly became deformed and turned into what are essentially eldritch zombie robots straight out of a Joy of creation game.
The war would quickly end soon afterwards as no one could no longer die and getting their sparks back was a much bigger priority. So after centuries of searching they eventually come across Earth to see their sparks now possess the form of a small organic. Despite the huge shock of it all cybertronians weren't going to back down but humans/the sparks weren't going to make it easy for them, they had A LOT to make up for. Even if humanity couldn't exactly remember why that is.
Made more difficult by the fact that almost every human thought Cybertronians look terrifying. (Can't blame them for that tbh.)
In my mind this could go one of two major ways, one, where you take pre-existing human characters (or ocs) and turn them into sparks, or two, do a humanized version of the bots as sparks. There's lots of fun things you do with both options; off the top of my head imagine Starscream trying to impress human Starscream, wouldn't that be messy? You could have your favorite human tear into Megatron for all he's done. Man imagine your own soul calling you out for being a terrible person. 💀
Optimus probably wouldn't even try to search for his spark, believing he's unworthy of it or something and if they did show up I could see him even avoiding the human.
But the main thing about this that appeals to me is the pinning, (romantic or platonic), just the sheer about of heart crushing pinning. Cybertronians would just be so pathetic, utterly miserable, they just feel so empty and hallow inside; wanting nothing more to cradle their humans inside themselves.
If you do a self insert you could explore themes of self love and the fantasy of deeply loving yourself. Selfshipping perhaps lol?
