Pheles is a lord who once loved and still loves a human, Johan. In order to be able to be with him forever, together they created the most precious treasure in Guze, a Treasure that can grant eternity to the Mystes bearing it: the Reiji Maigo. Due to the Reiji Maigo, she doesn't have to consume other humans' power of existence; she can get enough to survive from Johan without him being in danger of disappearing. Due to a fight against the Bal Masque's assassin Sabrac that severely wounded Johan, she sealed her lover into the Reiji Maigo. She was unaware that Sabrac had also placed the Silver into the Hougu simultaneously. The Reiji Maigo was then lost, so now she searches for him everywhere　with an Unrestricted Method "The Wheel of Wind" (Kaze no Tenrin), a guiding beacon that becomes a duplicate of her own when the target is found. In the light novels, Johan commandeers Yuuji's body to persuade her from sacrificing the current Mystes to bring him back and Pheles agrees to her lover's wish before leaving for parts unknown.

She is friends with Wilhelmina who once she had saved from the trap set by the Denizen Lord Sabrac. She does not appear in the first season of the anime but appears in the second season around the end of episode twelve amid her search for the Reiji Maigo

(Source: Wikipedia)