Ciel Sulfur/Biography

A Prime Field Device and member of the Mitsurugi Agency who wields the BlazBlue Alternative. Ciel was taken aboard the Dimensional Boundary Submersible Warship Fugaku by Kagami Hajou after their Possibility was erased. Together with Raabe, Ciel Dives into Phantom Fields controlled by Observers in the hopes of freeing them and gaining insight on how to restore the Possibility that was lost.

Alternative: Dark War
Ciel and Raabe arrived into a Phantom Field that was set in the Magister's City of Ishana prior to its involvement in the Dark War. Ciel found herself fighting against Another Dark Mai, and the two locked into battle. A person interrupted their fight, and Mai went to attack them - as this happened, the person subconsciously used Phenomenon Intervention. Mai was distracted so Ciel took the opportunity to escape with the person and run to a safe location. Ciel mentally connected with them and she learned that their name is Rei. Ciel promised to protect them after introducing herself. As Rei awoke, Ciel hurried them to their feet, hoping to get them out of harms way since monsters were flooding towards Ciel and Raabe as they were Contaminants within the Field. Kazuma Kval found the trio, recognizing Rei and asking them if they were okay. Surrounded, Ciel and Kazuma fought against the monsters until there were none left.

As the monsters evaporated, Ciel noticed that Rei was an Observer. Another Dark Mai leapt down near the trio, and Ciel hurried Rei behind her. As the trio had just been attacked by monsters, Ciel carefully approached Mai and asked her if she was an enemy. Mai did not take well to the question, instead introducing herself as a "villain" and threatening to stab Rei repeatedly. Ciel asked Rei that they don't Observe Another Dark Mai too closely, and that she will protect them from her. Mai threatened to kill Kazuma, Ciel, and Rei, so Ciel shifted to a combat stance and asked that Kazuma take Rei far from the current location. In that moment, however, Raabe used Phenomenon Intervention and moved the group away from Another Dark Mai and onto another section of the island.

In the new area, Ciel noticed that Raabe had deactivated so started to hit it to try and reactivate it. Kazuma believed that they had been teleported, but Ciel clarified that it was just Phenomenon Intervention. Kazuma continued to probe, asking who Ciel is and where she is from. Ciel clarified that she was not from the island, but from the Mitsurugi Agency, who were investigating Ishana and an anomaly within it. Kazuma, having also noticed how different the island was to what he remembered, agreed to help Ciel in discovering the cauldron within the island. The group then moved further into the island to begin their search. Ciel listened in on Kazuma's explanation to Rei about Ishana and the Mage's Guild, but listening in had caused her to ignore her surroundings. She interrupted the explanation as the group were surrounded by monsters which they fought off.

During the battle, Ciel and Rei summoned Units. Kazuma asked what they were, so Ciel explained: by using her ability to organize data and combining it with Rei's Observational powers, they are able to utilize Chrono Phantasma (Those Who Should Not Exist) to fight for them. In order to avoid the coming waves of monsters, the group headed towards north-east towards the island port where communications would be. When they arrived, there were no ships, no people, and a communication device which was not working for mysterious reasons. A scream pierced the silence and Ciel, failing to convince Rei to stay back and out of trouble, followed the source of the scream, trailing behind both Rei and Kazuma. After battling away more monsters, they found Trinity Glassfille. She introduced herself and explained that Ishana's barrier had disappeared, so she went to investigate, and that there was supposedly a secondary defence mechanism that causes Ishana to isolate itself in another dimension. Knowing that Another Dark Mai was currently stalking Ishana to find and kill the group, they decided to head towards the Great Library to find a way to deactivate the mechanism and get off the island.

Trinity suggested that the group go through the sewerage of the island in order to avoid monsters and Mai. As they ventured through the sewers, Ciel tried to explain to Kazuma and Trinity that she was there to save them, but she struggled to find the words before they were surrounded by more monsters. When they came out of the sewer, they arrived in a park, again surrounded by monsters which they fought off. As the battle ended, the group walked up past the park - Trinity revealed that she had been here earlier but had lost consciousness before reawakening in a forest. Ciel had questions, but kept them to herself. As the group made their way towards the Great Library, they went past the Grand Clock; both Ciel and Kazuma saw it pointing at 3pm, while Trinity could see pointing past midnight. Ciel's suspicions about Trinity being the Observer of the field were growing.

Inside the Great Library, Ciel was stunned by the sheer volume of books. In order for Trinity to gain information to help Ishana, they had to enter a forbidden section of the library, activating a security system which the group had to fight. Once the battle ended, Trinity admitted she was hesitant to let Ciel inside the area since she is an outsider, but Kazuma managed to persuade Trinity to allow her in. Once inside the restricted section, the group scrambled to find as much information as possible. Ciel then theorized that the group could escape by going to the cauldron, something that she knew existed in Ishana because of records she had previously read in the Mitsurugi Agency. Trinity continued to bring up Konoe A. Mercury, someone else that Ciel had records on. On Ciel's advice, the group headed towards the cauldron, which lay in a sacred area to the Ishanan population - the Ishana Cathedral.

As the group made their way to the Cathedral, Trinity voiced concerns over whether the cauldron actually existed. It was here that Ciel confessed that she was going to destroy the cauldron. Trinity and Kazuma became suspicious of her, but Rei voiced their faith in her, leading the two mages to realize that she has only helped them since they met. Rei's faith in Ciel made her happy, and the group headed further into the Cathedral after fighting off more monsters. When they came near the cauldron, both Ciel and Kazuma told Trinity that they had deduced she was the Observer, and that Ishana had become like this because of an interference with her Observation. The entire island was just a construction of her Observation, and that she needed to recognize the cauldron in order for it to activate. More monsters appeared and the group fought them off. They continued to fight down towards the cauldron, being blocked by monsters seemingly defending the cauldron from them.

When the group finally made it to the cauldron, they were met by Another Dark Mai, who was waiting for them. She gleefully greeted them, taunting Trinity and claiming that she had killed her earlier on, but due to the nature of Phantom Fields, Trinity was resurrected and her memories wiped. Ciel asked her why she was interfering this much within this Phantom Field, but Mai danced around the question, saying that she had noticed some interesting things, referring to either Ciel or Rei. In order to test their strength, Mai challenged them to battle; once the dust settled, she remarked that she had seen enough and disappeared through the cauldron. Trinity then turned on the group, unable to let the cauldron be destroyed and for her desires to slip through her fingers. Ciel, Kazuma, and the summoned units fought against her, eventually winning. Ciel then activated her BlazBlue Alternative to destroy the cauldron and free Trinity from the Phantom Field. Trinity, coming to her senses, thanked Ciel. Ciel bode Kazuma and Trinity farewell as the Field began to reform into a Possibility. Just as she was about to return to the Fugaku, Ciel took Rei with her.