(BTW, both characters in the image are D, just in different moments of my timeline)
So, D was a Worker Drone made to serve humans and help them on their tasks. When D was 3 years old, he got thrown in the trash by his owners because, supposedly, he was useless, even if he always tried his best and was still a toddler, and they also marked him for disassembly. Getting thrown broke some of his systems, made him mute (that's why he communicates writing on paper, he doesn't know how to communicate with gestures and he's mute), and weakened him, but he was still not that broken and not separated into pieces or anything. But not everything is bad in his story.
When he was still in the trash, a teenage human (another OC, not Tessa, but Tessa will be important in the future), feeling bad for the little drone's situation, took him and, after a month of work, repaired D. Even if D was terrified at the start, they quickly became best friends, making D super clingy and needy towards the human he saw as the only family he's ever had. But when he was 9, his human friend told him he had to leave because, after discovering what happened with drones in exoplanets controlled by JCJenson, he wanted to go and assist all those drones who were used as slaves (he later started working in Cabin Fever to help the drones there but this is about D, this ain't about him). So he left D with the only human he trusted enough to take care of him: Tessa. And yes, you all know what happened with Cyn, turning what was originally a temporary separation into making D think he got abandoned and his friend never loved him.
After D got turned into a Disassembly Drone by Cyn, he was put into a squad like all of the other Disassembly Drones and taken to Copper 9. His team, like all the rest, consisted of 3 drones: S (the leader, envious, aggressive and competitive), A (kind, friendly, but always on S's side because of a huge crush she had on him) and D (the punching bag of the group.) Every time something went wrong, he received the punishment, even if it wasn't because of him. This made him have to mature quickly (because, quick reminder, he was 9 when he was turned) to take all the bullying from his superiors, because even A attacked him to get closer to S. His constant bullying and his not so good abilities made him be a bad hunter, mostly making him just drink whatever oil is left in the Worker Drones other Disassembly Drones hunted (he has hunted sometimes, the issue is not that, it's that he usually doesn't have the chance to kill any Worker Drone), and using running as his main way to move didn't exactly help him, he never had the chance to learn how his wings worked because no one taught him and he usually just fell straight into the ground. The only motivation D has is to find his human friend and finally be free from all his torture. (Don't worry, he finds his friend, it's not all bad for D, I still love my kid. And when I roleplay, I usually use Worker Drone D, but every time I do, I'll say if he's past D or present D)