Thorn grew up in a secluded woodland and from childhood has worked as a servant for a mysterious figure known only as the Witch. Thorn's job involved looking after the woods and creatures within it, gathering ingredients, and other odd jobs that the Witch needed doing. Currently, Thorn works as a delivery courier. They were recently fired from their job, though this hasn't stopped them from delivering mail (and other things). Some of the mail is stolen from elsewhere, some is mail they've been paid to deliver, and some is not mail at all - just a feeling Thorn has that the item will be useful to its recipient someday.
The Witch has been absent for 5 years now, leaving behind a small parcel when she disappeared. Thorn hopes that delivering the Witch's parcel might help them find out what happened to her.
Thorn met her mentor, Clementine, in the facility, where she learned that Clementine was a clone of Eleanor Halliday. She also learned that the package she thought was for her was actually not, and that she would know who it was for when the time came.
She later found out that her package was for Mani, when she regained her memories and Thorn got a sense that it was for her. It turned out to contain Mani's biokey, the sixth and final one they needed.