In short, her time there was comprised of being berated and kept alone in her room as to not harm any with her “witch powers”. When let out on occasion to socialize, she made a friend (a drow) who spoke of the wonders of the dark. Hester loved to hear their stories. Soon after, Hester was attacked by another patient in the ward who happened to be a dhampir being kept there for “witchlike tendencies” as well. It was then that Hester was fully isolated, being called a danger to society. To this day, she has never fed on blood. Only ever knowing the emptiness of life without being fed properly.
In the asylum, Hester had learned how to sneak around and hide items in her room. She used these skills to hoard books on magic, wanting to read up on them to better control what she calls her “witchcraft”.
One night, when Hester snuck out to retrieve a book, she caught sight of the hound once more. When does anyone not follow a big spooky dog? She managed to break out by attacking a few staff members and killing them. She ran away straight in one direction, following the dog, and didn’t stop until she reached the nearest town. Since then, she’s become a nomad with a fascination with medical procedures she had witnessed and been part of. It’s her way of coping with her trauma and it’s something she enjoys greatly.
There's a part of her trauma that stuck with her after the Mist. Although she doesn't remember much about how she got there, she knows there's something up with the fact that she doesn't have memories past a few weeks ago. She has no way of accessing them, but it is rightfully distressing.