Born to the unicorn Amaterasu and the shadow-beast Anju, Arcadia was not exactly a planned foal. When she was in her basket, her biological father attempted to steal her and her two brothers from her mother -- luckily, he only got away with her two brothers. Unfortunately, during the struggle, Arcadia's basket was lost and Amaterasu, in her despair, was unable to find her again. Her basket was discovered by a unicorn named Nymphadora Tonks, who took her back to Mingan Kishi's teepee. With the help of the two-legger, Tonks, and Barnacle, the three of them helped to raise the young abandoned unicorn into what she is today. Raised by anyone else, the little filly might have turned out differently -- but she was never lacking for love and attention, and what could have made for a dark, evil mare, Arcadia grew up sweet and kind.