it's fixed NPC. You can find her in one of cells.
Which cell? I've tried looking everywhere in the cellblock and I couldn't find any button prompts.
Go south wards after having enough level(5 level I think?)
Tell me does any of the clues you have gathered describe any of the fixed NPCs?
If so go and talk to them.
You need to become friends with certain cat. Her name is Rahi. When she is your friend, you can visit her cell and ask for this item.
You can ask her about it if she is still at her bench too.
