I have a rogue character with the Haunted One background from Strahd with a whole description and backstory already worked out. At the risk of overloading you with the first application, I'll stick it below (the longer bits in Spoiler tags, of course).
Riz stands at 2’ 7" tall, small even for her race, and is gaunt, weighing in at 36 pounds. But beyond these simple measurements, the trauma that RIz has suffered has made its mark on her features, draining her face and hair of any vital colour and forever giving her eyes a haunted sheen. She habitually wears black, both in mourning and because it helps her to hide.
Her apparent frailty belies the strength in her bones, a strength borne of her indomitable willpower. Riz pursues the evils of the world in a self-imposed quest to prevent other children from having to suffer the things that she went through. She never flinches from danger, knowing that she has been through the worst that this world can offer, and that death would only mean peace for her.
[ +- ] Background
Once, Riz was a normal halfling girl; reckless, humble and carefree. She remembers those summers as though they are a dream, just fading after wakening; brighter, happier and more vibrant than she now believes possible. She was born into the living arms of Jojo and Renwise Burrowes of Norden, a mostly halfling village on a river island several miles in from the sea. A small punted ferry was used to transport goods and passengers to the shore, but most people stayed on Norden Island, they had almost everything that they could need there.
Renwise was the local miller, and as such was held in high esteem in the village. He was a well-muscled, jolly man with a large bushy moustache wider by half than his face. He seemed to take any challenges he was faced with in his stride, and with a healthy dose of humour. The only thing, in fact, that he was serious about was his work, which he approached in a no-nonsense, methodical way. Between his position and his humour he wasn’t without female admirers in the village.
Which is why everyone had been surprised when he announced his engagement to Jojo Wainsmith, an itinerant young halfling who described herself as an "adventurer". She had swept into town, throwing money around which she had acquired from who-knows-where, and had caused more than a little fuss with her bawdy stories and uncouth ways. Most of the village were determined to just ignore her until she went away, but with the engagement that suddenly seemed an unlikely eventuality. It was only in Autumn three years later, with Renwise’s family running out of reasons to delay the wedding, when something happened which would make the village appreciate what Jojo had to offer.
A flock of winged kobolds descended on the village, determined to raid the newly harvested crops. The alarm was raised late, due to the pickets posted at the river being called away somewhere to the north, and so the monsters were on them before many could get into their fortified cellars. Jojo, it was said, emerged from the tavern holding a flagon of ale and a chicken leg, with a grin on her face, and drew the sword she had been carrying around. With a great cry she charged the nearest kobold and, taking him by surprise, drove him through the doorway of an apothecary and cut him to ribbons. She gathered any folks she found around her, organised them, and managed to get them to the town hall where there was a modest armoury. The villagers were surprised to find that the ferocity of their opponents was easily countered by a resolute and organised defence, and the village managed to drive off the raiders with relatively light losses.
The entire village attended the wedding and the meal was talked about fondly for many years afterwards. But Jojo was getting restless. Village life didn’t suit her and she was soon climbing the walls. Some speculated that her decision to have a baby was more to break the monotony than anything else. Even after Riz was born, Jojo would take her for long walks, often along the banks of the river, talking to any pickets they met about whatever action they had seen. When Riz was old enough to start attending the community play school, Riz took a job scouting on the mainland to identify threats before they materialised. She was often away for weeks, or even months, but when she returned it was always the best times for young Riz.
Just after Riz’s sixth birthday, Jojo went beyond the river again. Life carried on as normal, but when Jojo wasn’t back after six months people started to talk. Riz’s behaviour deteriorated, she would throw tantrums for the slightest thing and took to playing on her own. Renwise often found her playing with her stuffed animals, getting them to attack their garden wall and getting cut down like the wheat in the fields.
When Riz was nine, Renwise announced he was going to remarry. The village made every effort to talk the occasion up, but nobody really believed that the miller had ever really got over the loss of his first wife; where once he had been ready with a joke at all times, now he would grouch and grumble his way through the day. No more than a month before the wedding, a storm hit the village. Rain pelted the grassy roofs of the houses, running down in thick rivulets and washing any loose items away down the street. Lightning struck at the trees all around, starting small fires which were soon doused by the downpour. But worst was the wind, which howled and moaned like the angry ghosts of the dead, come to have their revenge on those still warm.
Renwise sat in his rocking chair and stared at the wall, listening to the din. Juse Florrygale, his fiancé, bustled around, preparing meals and trying to be jolly and generally annoying Riz even more than usual. A door slammed as the wind blew it open, and Juse rushed away to secure it. The next thing to be heard was a horrible scream, which finally moved Renwise from his reverie. He leapt from his chair and rushed through to find his fiancé shrieking at an apparition standing dripping in the doorway. A dark form, with hollow, sunken eyes and a gruesome expression, just standing there, clutching a bundle of rags in front of it. When Riz came through and saw the figure she immediately burst into tears and rushed forward, she clutched at her mother’s soaking clothes and moved to embrace her, but Jojo shied away.
"Stop," she croaked, "Look."
And Riz saw the bundle in her arms was a baby.
Jojo and the baby, Yorla, settled into the spare room of the mill house. Juse went back with her parents and the wedding was called off, but bad blood was now brewing between the Burrowes’ and the Florrygales. The baby was sickly, and for many months seemed to be right on the verge of death. But somehow she pulled through.
Things didn’t really improve for Riz after that. Her father was only ever seen working in the mill or drinking until he passed out in Dunston’s Tap House. Jojo had again taken to going for long walks, leaving the care of Yorla to Riz. None of the Burrowes clan offered to help, even when Riz begged they refused. So Riz had to grow up fast. Her new step-sister was a strange girl, but who could blame her under the circumstances. She had no guidance, except from a big sister who openly resented her. And she grew fast. By four years old she was already nearly as big as thirteen year old Riz, who had to find ever more ingenious ways to control her.
Jojo never really looked like her old self. She seemed to have aged decades in the three years she had been absent, but now it seemed that Renwise was catching up on her. His hair thinned rapidly, and his once taught muscles ran to fat. The talk in the house never ran to any frivolities, merely necessities. The four occupants seemed to haunt the place, rather than live there. Relations in the village weren’t any better, as most of their neighbours openly shunned the family.
As Riz neared her fourteenth birthday she dreamed about escape, about going to the city and being in among people who really lived, who didn’t know who Riz was and so wouldn’t judge her for her past. She even went so far as to prepare a small pack for that day, soon, when she would run away, and they would never see her again.
That day would come sooner than she knew.
One hot summer day Riz was returning from the river, water still dripping from her long hair, when she noticed the first signs that something was wrong. It was the smell which had clued her in, she would later muse. It was a heady, sweet, metallic aroma, and it carried all the way to the end of the street. Riz walked in the front door of the family house cautiously, hearing nothing within.
"Hello?" she called, trying to keep the worry out of her voice, "Where is everyone?"
"Riss!" came Yorla’s voice from the kitchen. She sounded happy.
Riz shrugged and headed for the kitchen, pushing open the door… only to stop short. What she saw was… she had no words.
Her hulking great toddler step-sister covered in red, like most of the room, and chewing on some kind of smooth pink meat, which she followed with her eyes down to the body of her father, the "meat" turned out to be a section of his entrails, which had spilled out all over the floor. Yorla cooed happily at Riz, whose stomach rebelled. She turned quickly away and threw up in the hall.
Then she heard a noise from the other side of the kitchen. She turned back to see a woman, if you could call her that, an aged, blackened old crone, stooping low to avoid the ceiling of the room. She was standing over the body of Riz’s mother, a look off gleeful avarice on her face. The hag’s red eyes turned to Riz, she smiled and gestured for her to come closer, and Riz could feel her body moving of its own volition.
No, she thought, NOOOO!
She managed to tear herself away and went running back out of the front door, out of her own garden and into a neighbour’s, where she hid behind a tree and tried to get her breath.
Her neighbours found her sitting there, panting, wide-eyed and making no sense and they tried to chase her from their property, but she wouldn’t go. Kendrick, their middle son, was sent to Riz’s house to fetch Renwise, and it was at this point that Riz came to her senses. She screamed at them to keep the boy here, but nobody listened to the raving lunatic on their lawn.
The events of the rest of that evening were grim indeed. After hearing the screams of poor Kendrick, a mob was assembled to investigate the cottage. Brandishing whatever weapons they could find, the motley group advanced on the mill house. Just as they entered the grounds, the hag emerged from the doorway, young Yorla peeking from behind her, and stood to her full height. The mob pulled back in fright, but the hag just smiled and unleashed dark magics on all of them. She raised a resounding keening wail which carried over the roofs of the houses to every corner of Norden Island. The people of the village cried out in anguish, clawing at their ears to make it stop, but worst of all was that the sound seemed to draw them on. Every villager marched glassy-eyed towards the Burrowes house, to be welcomed by the hag, who slit their throats and filled small flasks with the blood of each one.
Only Riz, either because she had already tasted the hag’s magic or because she was out of her mind with grief, managed to resist the call.
She ran off into the night, just running with no goal in mind. Eventually she splashed into the river at the other side of the island, but she didn’t stop. It was only two days later a cold and hungry Riz managed to muster the courage to return to the village. She found the rotting corpses arranged in macabre sculptures of bone and purifying flesh. The hag and Yorla were nowhere to be seen. She then left Norden behind. She was going into the wilds. She would track down her step-sister and either rescue her or… Well, one thing at a time.
Riz spent the next few years scouring the countryside, but never found any sign of Yorla or the hag. She became strong, and found ways to hide from any creatures she couldn’t defeat. But as time drew on and she got no closer to finding her quarry she became dejected. She never thought about her time in the village, to do so invited despair, and the memories became hard to access. After a couple of years, if asked, she could tell you she was from Norden, she could describe her early life, but then her mind would slip back to the here-and-now, her life in the wilds. The time in between was slippery, mercurial. She just knew that she had to find Yorla, and that she would know her when she finally found her.
Eventually she stumbled across a skirmish between a small group of people and some goblins. She watched the people defeat the goblins and tend to each others’ wounds. These people reminded her of the good days, but she didn’t want to approach them. Instead she let them go, and tracked them from a distance. She lost their trail some ways south, but kept exploring the region, and soon she discovered the high stone walls of another settlement. This was no village, like Norden. These walls looked high and imposing, and safe.