(This is for the fanfiction "Crossover Together". Info may change from canon information)
Aleistor Chamber is an aristocratic, handsome man and leader of the elusive Aurora Society.
Aleistor is an extremely handsome man, as commented by many nobles, with lavender eyes and light-blond hair that reportedly "shines like the sun."
Aleistor regularly dresses in elegant clothing which consists of a white suit, a pocket square, and an ascot tie, along with accessories such a brooch and white gloves.
Aleistor is a very pompous, narcissistic, and melodramatic man who compares things to people often, such as calling Ciel Phantomhive (as he was in disguise) as a robin. Additionally, Aleistor has a strong interest in black magic and resurrection, and studied into the arts during his youth enough to know that Demons existed at all.
While exact history is unclear, he mentions in studying black magic and the Underworld during his youth. His involvement in the Aurora society was enough to make him wanted by Elysium officials.
Not long after Ciel and Sebastian "join" the Aurora Society, Aleistor Chamber appeared before them in a phoenix pose simply because he wanted to present his. He warmly welcomed the newcomers into the society, a bit saddened to the fact Ciel's face was so damaged. When Ciel told him he hoped the society could cure him, he boasted that the society could do far more than that, and while he will find an appointment to make him beautiful again, he felt a presentation was in order first. He then proceeded to present his resurrection process to numerous others on the Campania, seemingly reviving Margaret Connor before everyone, him proclaiming that the phoenix had risen again.
He was brought to her family later on, asking about her behavior, and Aleistor reassured them that the effects were only temporary, and that she'll be back to normal in no time at all. He was fully confronted by Sebastian later on, and he revealed his true intentions to create a empire where not even death is something to fear, and that he will be the one to rule all of it once it goes worldwide. He boasted that he could defeat all oppose with a single glass of wine, which he then splashed on himself as a way to "freshen up" in presence of the devil. Turned out he mixed holy water with the wine, and Sebastian couldn't touch him. When Undertaker, Victoria, and Bardroy arrived, he gleefully welcomed them back with little worry. He soon called on his "army" of reanimated corpses with a specialized high-pitched whistle. He watched on from afar, feeling like the emperor Nero watching the "colosseum of corruption" (to the anger of everyone else). He soon found though that many of his corpses were already killed by Sombra, which only then terrified him.
It was revealed later on by Kyoya Ootori that Sebastian made a deal with Aleistor just before the final confrontation, and Sebastian gave him instruction on how to remove and transmutate a human's soul. Once everyone left, Aleistor extracted Sebastian's soul and placed it into the recently deceased Kyoya's body, giving Sebastian a new identity.