(This is for the fanfiction "Crossover Together". Info may change from canon information)
Ciel is a short, thirteen-year-old boy with bluish-black hair and rich, deep blue eyes. His arms and legs are thin, his shoulders slim and his waist narrow. Ciel typically dresses in a way that suits his noble standing, and he has a very extensive wardrobe. Ciel sports two rings: one, which he wears on his left thumb, is an ornate silver piece that holds an emerald-cut deep blue sapphire.
Throughout much of his appearances, he is mainly shown as a calm, and serious individual towards others. He doesn't treat others with much respect as he would give to the queen or his fellow workers, as he considers himself above most of them, and most of his goals he would do either benefit himself, or benefit the Queen, as his main reason for staying with Team Harmony at all was on request by the queen. He has shown a high level of maturity and intelligence for his age, mostly due to him living by himself and having control over the manor. As the Queen's guard dog, he has developed a natural talent for investigation.
As a young child, he was shown as a very innocent and fun-loving boy, almost a polar opposite to his older self. This was all destroyed after he and his twin brother was captured by a cult group, his innocence taken away from him. His involvement with the cult had left him with a case of PTSD - evident when he froze still when witnessing Hellgar's fire at the Queen's home, terrified of the flames.
Ciel Phantomhive grew up in luxury within the Phantomhive manor with his mother, father, twin brother and pet dog despite his parents being the Queen's guard dogs. He and his brother, by their ninth birthday, left their home as a birthday surprise, being a visit to the queen. By the time they got however, they found their parents killed, and they were captured by the cult group shortly afterwards.
Ciel himself woke up inside a cage, and throughout his days he was victim to numerous tests and tortures by the group. It was during this that he first met Sebastian, who offered him a contract to escape the place. He at first jotted this up to madness and refused, but as more time went by, and in desperation, he finally agreed to it, and summoned Sebastian to release him. This left him the contract in his eye.
Waking up one day to head to the market with Sebastian, Ciel took notice in Nagisa Shiota as he was heading home, asking Sebastian if he truly noticed anything different while there. Curious over Team Harmony, he decided to set up a get-together with them, having Sebastian invite them over to the Phantomhive manor. Upon their arrival, he had them brought over to the study so they could get to know eachother better. When his status as the earl was brought, he made it clear that his parents had died years ago, and that the status was naturally moved to him. He also suggested to change the subject, and soon they were brought to lunch. After lunch though, he ended up captured and taken away by Envy, who was disguised as a local crime boss to take Ciel for ransom. Ciel was rescued by the group shortly after.
After the encounter, he found Nagisa out the following night, and revealed his demonic involvement to him, along with Sebastian being a demon. He also offered for him and his friends to return to the manor for another chat, which he found out about Team Harmony's true motives the next day. After some discussion, Ciel Phantomhive took the time to bring the others to see Undertaker to be sure about his captor's whereabouts, just to find that he was dead. It took a bit to get some information out of him, but he and the others did find out about Envy and Lust Homunculus.
When finding out of Yugure Kagayaki and Sebastian's disappearance, he brought the others back to Undertaker to get some answers, finding the idea that they weren't dead yet. Ciel took the time to try and find them, though acting like he wanted to punish Sebastian instead of missing him. During his attempts to find them did he and the others of Team Harmony receive invitation to the Royal Ball. He decided to go on the threat that some Demons would be there as well, and that they had to keep the guests safe. He was in disguise as a women like Nagisa Shiota, under the identity as "Izzie Florahorn", one of Pinke Pie's two daughters. During the investigation, he ended up running into Victoria, who immediately found him out but allowed him to continue his investigation.
After the royal ball, he met with Seitenshi and The Queen for the initial exchange in information, and agreed to share information about the protection agreement to the others. He had much of his servants guard the manor as he joined team harmony for guarding the queen, when Hellgar arrived. He himself didn't fight all too much, but became isolated with Yugure when the fire broke out within, triggering his PTSD. He was later rescued by Sebastian on his return alongside Yugure.
After the night, the queen had him under her instruction to help Team Harmony in any way he could.
Before Team Harmony could go back to japan, Ciel and Sebadstian got them into an investigation towards Amestris on possible demon activity going on at Central, and that they should go and see what was going on. In their arrival, he explained the situation to King Bradley, and was allowed to stay and see to it that whatever activity was going on would be handled. He took on a supporting role during the ordeal, and during the Pluton incident.
After the attack, he and the others went with Edward Elric and Alphonse Elric to a home outside of the main city when they find Envy with them. He took it in stride, and suggested that they keep him in their team as it was far better than having him constantly hunt them down. This same idea was put into play sometime later when he met Gaara, and him lying to Gaara as he too had his life ruined by Tirek, and making their goals align. By the end, he went back home to England.
After much of Team Harmony returned to Japan, he had managed to get hold of their contacts and phone numbers, as he at first felt it was a more efficient way to keep in touch with the team. This became less needed though when Korosensei had him enrolled in Orora High School as a E student, alongside Edward Elric and Alphonse Elric. During this, Gakuho tried to get him to go up a few grades to a higher class, but he refused as he didn't consider it as efficient to him.
When he was told about the upcoming future sights from Nagisa Shiota, Ciel Phantomhive confronted Gakuho Asano before he could shoot anyone, getting Gakuho to tell him about Rikuto Ikeda. He found this amusing however, to the point of laughing himself silly, and then told Gakuho Asano his own backstory. Once finishing, he stated that "Hell took everything away from him, yet it was hell who gave him a second chance", and he considered himself a "cursed child". He tells Gakuho how he was talking about hell yet never truly saw it himself, and he found it funny how it took so little for a full grown man to break, whereas a child like him got through his trauma fairly alright, winning against him and saving Heine's life.
When the group split apart, he went with Alphonse Elric and Sebastian Michaelis onto the Campania to confront Aleistor Chamber. He soon discovered that Bardroy and Victoria had joined them on the Campania as well, and gave Ciel Phantomhyive just enough information to lead him and Sebastian to the Aurora Society. He and Sebastian just manage to get in, him disguised as a young child in hopes the society could cure him of his missing eye (and a ventriloquist for Alphonse Elric's involvement). After seeing the result of Margaret Connor, he at first was left impressed, but when Alphonse pointed out he only revived the body, not the person, he sent Sebastian off to investigate. Alphonse later asked him if he would alter a dead relative's memories if he would find a way to suit him, to which Ciel stated that he would, and he would remove any negative traits to make them better for him. He questioned Alphonse about it, and in the end confirmed that Alphonse was jumping to conclusions just before Sebastian came back. Once they confront Aleistor however, they found Sombra had arrived as well. It was during this that Ciel had his soul taken by Sebastian, and the remainder of him taken to the Underworld.
He woke up and found himself inside Abaddon, and in a panic, pleaded for someone to break him out, and rescue him. His trauma also came back up to the point when he felt almost sick.
Ciel remained isolated in his cage, refusing to eat and stating that he'd rather die than stay in such a horrid place, starving himself. However (and to his dismay), his body was revived only so he would live out his sentence, the imps suggesting to hold off killing himself until afterwards. During his stay, he was brought to the main lobby with the rest of the team to be used as bait for Nagisa and his remaining friends. His PTSD kicked in again when the firest of abaddon turned on at Sombra, Chrysalis, and the Slicer Brothers' arrival, making him completely panic. He was unable to escape from Abaddon until Nagisa had arrived and busted him out. Upon returning, he held a funeral for Sebastian, leaving him a blue rose at his grave.
Sometime after his return, he jotted up Sebastian's attempt as him simply finding an easy way out, and nothing more. When he found out Kyoya Ootori was truly Sebastian, and immediately confronted him about this act he pulled, and demanding him to come back to work, just to find that he no longer worked for him. Ciel simply stated that Sebastian "wanted a new job", and that he never died at all. In an ironic twist, Ciel ended up under Kyoya's teachings in combat training. After Nagisa showed what happened to the cult group that tortured him, Ciel figured that Sebastian wanted to milk his role for what it was worth, but later on confronted him about it anyway and that he would've killed himself regardless of what happened. He found out about Sebastian's true motives for all of it, and Ciel simply tossed a crumbled up picture of the cult, and ordered Kyoya to clean it up. He got word of Heine's return just before he left.
For the final fight, Ciel had to keep out of it and guard Lugia as a final line of defense. When Sombra did find them, he brought up Sombra's past, and considered going through all of this for one angel as pathetic. When he heard what Sombra thought of humans, he actually laughed at the fact that he thought Sombra was just a clever twat, and yet actually figured humans out. He went on to explain how humans trample eachother, and that they're more demonic than Demons. In the end, he pointed out how he too was human, and that all the horrid behavior was just how humans are.
After the final fight, he was seen amongst the crowds during Team Harmony's graduation.