One of the Trinity of the Bal Masqué. Bel Peol is entitled as the "Strategist" of the group.
She's the only Trinity left, and she disband Bal Masque.
Bel Peol wears a grey gown with furs, a necklace, a pair of earings, and a pair of high heels. She has three golden eyes — one on her forehead — and she covers her right eye with an eye-patch. She has a long hair with red (not exactly red actually) color. She usually brings her chain treasure tool Tartaros with her.
She doesn't have any qualms in manipulating her subordinates and sending them off to die. Apparently she also has a gift for engendering loyalty in her subordinates, Vine is the example, as she is capable of inspiring them to perform obviously dangerous tasks on her behalf. Her strategic skills are balanced by a considerable aptitude for combat. She's quite strange, like something that doesn't go with her plan, because for her it's make life more interesting.
In the third season, she shows affection towards Yuji. Maybe this is not because of Yuji himself, but because of the Snake of the Festival.
She has three eyes, and she covers her right eye, which she has lost it in the Ancient War (the sealing of the SoF). Actually she is the one that took it out and sent it to him, so that his master can return. Her eye is known as the Banner, which is the transmitter for the Snake to send his special Unrestricted Spell, Psalm of Grand Order, to his Priestess and perform the famous "Grand Order".
She then accompanies her master and other Denizens through the Path of Pilgrimage, the road to the Snake's true body inside the rift. With Hecate's ability to link with her right eye, the group successfully locates and revives the body and Bel Peol gets her eye back. During the return, they fought Shana's group and she fails to save Sabrac who deny her assistance and perished. After they come back from the rift, Bal Masqué becomes victorious over Flame Haze Army and they moves to Misaki City to perform the ritual to create Xanadu.
After their long yearned plan successes, Bel Peol uses Tartaros to separate the Snake of the Festival and Yūji. She crosses to the newly created world, Xanadu. As the the only Trinity left, she ordered the disband of Bal Masqué and wonder the world, waiting her master's next return indicating Bal Masqué will be reestablish once again.
Bel Peol normally aims the first attack on the face of her enemy. When her enemy is caught off guard by the distraction, the second one goes straight towards the upper part of the belly. This strategy was used when she fought Wilhelmina Carmel. The latter was then defeated and humiliated after receving merely two shots to the belly. Bel Peol also used this ability against Shana while they fought in the Gemini.
Bel Peol's primary Treasure Tool is a length of chain. It has the ability to store an army of Rinne inside which is very convenient when going on battle. Another ability is to deny the cause and effect of any thing it binds including sealing off Flame Haze abilities. Bel Peol used it to seal Shana's ability when she was captured to Seireiden. It is one of the three instruments for the Grand Order.