Deepened (Finale To My Darkness)
Quick Author's Note, this does come in the time period of season three in Transformers Prime, but I personally think Optimus is super fat after his 'update' so in this, he's not. For all you all who have seen the live action movies, to be able to fly, he's going to have the jets on his pedes instead and basically keeps his original look. And no fat muscle car. Thanks.
The former Shadow Sisters have been forced to become Decepticons after the destruction of the Autobots in the fiasco with the Omega Keys. However, when they are reunited with the Autobots, things are different between them.
Starfreeze is still reluctant to give her spark fully to Optimus out of fear that he could be manipulated because of her, though he tries to convince her of his power to keep her and himself safe. This threatens to crush them both as the war with the Decepticons rages on.
Skywave and Bumblebee are happy to be together again, but things seem to be different with them. But, as the Decepticons continue to attack and raid, protecting each other seems to bring them closer than they've ever been.
Along with additional love interests in Team Prime, the darkness that Starfreeze and Skywave relied upon is returning, though not only in themselves but a certain human. The sisters try and help him, but soon give up trying to rid it and help him instead to control it. Though his life may never return to normal if he becomes one with his new power.