Boneset

Boneset, a fourth-born sibling who never expected to make much relevance in the war, just a simple follower of his Bigwing, in a relatively poor part of the Mud Kingdom (not the Diamond Spray Delta, but certainly not middle-class) who had a relatively cozy and stable family with four other siblings, despite it being war, they were a unit together. However, Boneset was especially close to the sibling who hatched right after him, Trumpet (short for Trumpetweed), who was a bombastic noisemaker of a personality and wanted to make a glorious name for herself. They got along like peanut butter and jam, despite the personality discrepancies, Boneset being a healer and Trumpet being the warrior, them having hopes for this war being over soon and Trumpet protecting Boneset while Boneset patched her right back up.

Until Trumpet died in a senseless charge against the SeaWings ordered by a serjeant who thought aggression was the best defense. Everyone else managed to survive, but not Trumpet, who wanted to slay the head of the SeaWings and stopped the battle right there and then. And Boneset spent Trumpet's last moments trying to hold back all the blood loss from a spear in her chest while Trumpet's eyes clouded, making sure he would never forget that helplessness and lack of control and deep, *deep* anger against fate, destiny, the gods and nature for taking away his sweet little sister.

Right after that battle, he came across the serjeant who ordered the charge, badly injured and clearly walking with a limp from a spear stabbed in her thigh. It was dark and she wanted to get some fresh air and asked Boneset to help her take a walk. She started talking about how the charge didn't work out as well as she hoped against the sea snakes, not knowing Boneset's sibling was killed in it. Boneset growing angrier and more furious until the serjeant said this: "Aw, well. Mistakes happen, right?"

And Boneset grew quiet. He picked up a rock... and bashed her skull in. And kept bashing it in. Until her skull was a wreckage of bone and blood.

Once he stopped, huffing and puffing, he realized the enormity of what he had done and ran off to his Bigwing, crying about the incident and what he had done. She tried to comfort Boneset, completely understanding why he had done what he done... but the damage was done. Right now, they had to cover their tracks. They tied the body with rocks and dumped the body into a swamp, hoping no one would notice the body at the marsh's bottom, but Boneset was still haunted, especially as the next day broke and everyone wondered where the serjeant was... considering she was a sibling group's Bigwing.

Only the Bigwing and Boneset knew, but it never left Boneset. And it got worse when another battle commenced... and that serjeant's sibling group was killed and only the youngest of them survived it. Leaving Boneset with even more guilt and questions about fate and destiny and how an originally irrelevant fourth-born forever changed the course of a family and broke it to the last member. With his Bigwing's permission, Boneset's group immediately took in that survivor as an unsib. The Bigwing, out of understanding, Boneset, out of guilt and need for redemption for what he did.

Yet, whenever he actually looked at his unsib, the guilt grew too much and he became aloof and snappish, triggered and flooded with terrible memories of his own lost sister and the murder of that serjeant. So he decided to go to the Jade Mountain Academy out of a need to escape the trauma and haunted memories, his Bigwing  giving him full permission. So. There you have it, Boneset, a quiet, mild-mannered, studious fourth-born sibling who tries to take life's sanctity upon most costs, but one hell of a quiet temper and a scornful attitude to fate and destiny and whatever greater powers are there. Because, if there are such things, what monstrous presences would let any of the tragedies befall him or that serjeant's siblings or not punish him for the crime he committed.