Deya first didn't know her name and thought it was Callista. She used to be one of the the trolls that were captured by King Arthur before becoming Trollhunter. Deya the Deliverer was a legendary Trollhunter known for exiling Gunmar and the other Gumm-Gumms to the Darklands during the Battle of Killahead and sealed the Killahead Bridge with the Amulet of Daylight. She was the most legendary Trollhunter after being the one who banished Gunmar to the Darklands.