Sepia is the person who lives on top of the mountain. She is very proficient at using a crossbow. She sometimes visits ruins with tall building to stock up on cans, but she doesn't do it as often as she used to due to her age. She claims she's no longer excited about seeing these ruins. She is Claw's friend and she taught her how to use weapons. She was the first person to witness Claw's "birth" , and briefly considered adopting her before the sovereigns took her.  She took a box from the asteroid but was unable to open it.
Her skin is yellow. She has gray hair and wrinkles, indicating her old age. She wears a light brown sweater and dark brown pants. She walks barefoot. When she was younger she was wearing the same clothes and her hair was ginger. She lives in what appears to be the same house as Sari's.
In the Tower
After being captured by the Sovereigns she woke up tied up next to Claw in a cell inside the Tower. Claw said she'd like to live with Sepia.