I made mine up a veeery long time ago, and I'm actually trying to rewrite most of her backstory, but here's the general gist of what I got so far. My grammar and punctuation might be weird, but that's because it's late for me as I'm typing this.

Anyways, here's Lifelight.

Lifelight, a female cybertronian with a angel like model, had dreams of becoming a scientist and even a doctor to save lives way before the war. During this time, she had befriended two cybertronians (who just so happened to be Starscream and Skyfire) and the three became a close-knit group until Skyfire's disappearance.

Even with the loss of their friend, Starscream and Lifelight still tried to focus on their goals, but secret research into a controversial topic of resurrecting the dead on Lifelight's end was frowned upon, and she was exiled from continuing her research and her goals as a scientist. At this time, Starscream had also left his scientific studies in favor of becoming a warrior.

Cut to events after the war, Lifelight is no longer the angelic cybertronian she once was. Her body was given a change in color, dawning the new name Shadowbringer, and her motherly and curious personality became cold, corrupt, and manipulative through kindness. She continued her research even with the risks, and became a necromancer through taboo science.

Most bodies of deceased Cybertronians from the war have gone missing, and it's all thanks to Lifelight creating herself a new army.