It's not known where Celeste came from but she was found by both a young Kurt and his Father Brutus running away from some Slave Traders, Brutus takes out the Traders and takes in Celeste, both him and his wife Sally accepts Celeste as their Daughter, Kurt becomes her protective step-brother and beats up anyone who harasses her, overtime Celeste has become tough on her own watching Wrestling on TV, she will sometimes Wrestle with Kurt training herself while painfully locking him in different ways, when Kurt lost control of his fire again Celeste was protected by her awakened Esper abilities that looks like Holy Light, this light can heal everyone around her and she can remove illnesses which gets the attention of the Solothurn Ballistic Church, they ask her to join them and she would be treated highly and be provided the proper wares for an Esper, they believe her abilities are from the Divine Realm and want to help her develop it, though Celeste would prefer to stay with the Styx Family Kurt recommends her to choose the Church so she can live more comfortably and live richly like the other Nuns

Praying and Training in the Solothurn Ballistic Church Celeste has learned in firing her Giant Ballistic Crucifix while keeping her distance and healing those around her, many of the Ballistic Nuns have Esper abilities that are considered holy but Celeste's ability is seen as the most unique and she is treated highly by Father Mauser who sees high potential in her, some of the Nuns seek to get close with Celeste, 1 wanting to sleep with her, the Church believe Espers are Divine Beings that have not yet Ascended yet to a Celestial State and Celeste herself is seen as an Angel, though she herself would prefer the life of a Female Wrestler and likes to be rebellious, though in front of other people and Father Mauser she behaves and acts like a proper Nun, she prays for people who are in need and is requested by many who seek treatment for illnesses, she deeply cares and will defend those in need, after becoming a full Ballistic Nun she was ready to go back home gifting Kurt with a Cross which he keeps on reminding him that he isn't a Demon, not realizing it is actually blessed by Celeste's power which scares the Demon within Kurt

Celeste's Esper Ability is a powerful light that shines from her body that can heal almost any injury and cure nearly any sickness, it can also boost another Esper's power but will strain Celeste if she overuses this, but to make sure this doesn't affect her she prays with light shining from the sky onto her which empowers her light causing her no strain, but this does leave her vulnerable and in need or protection, her light can also blind those around her when they look directly at her while she uses it, when enhancing another Esper their ability is much more greater and enters another stage that they normally cannot get to making her very special, it's not known where her power originates but it awakened from Kurt's fire protecting her from becoming ash, Celeste doesn't seem to drain her psychic energy but will get a headache from overuse

Her Weaponized Crucifix the Ballistic Testament was made for her by the Solothurn Ballistic Church to defend her from the Twisted, although it can form a stand so that Celeste can fire it she tends to not use it as she is oddly very strong and can carry and fire the Cross, on the long end it opens up with it's Rapid Machine Gun that can tear through the toughest armor and can take down vehicles, the other end opens up to a Rocket Launcher that can fire Rockets at high velocity, that parts on the side provide the ammunition for the Machine Gun and Rocket Launcher but can also detach and form into flying drones that defends Celeste and retrieve more munitions from Celeste, the Green Drone fires it's own rapid shots that can take out smaller enemies while stunning the more bigger ones, the Red Drone drops bombs on it's targets away from Celeste, while they are off she can still fire the Cross but with limited ammo, while not part of it's design Celeste can also slam the Cross on her enemies using it's weight to crush them, when not in use it will float behind her following her around