Citadel is a Montauk Experimental, similar to Coventore. He was created to function as a living nuclear reactor. His muscles bulge and throb unevenly from the nuclear energy they produce. Under normal conditions, he's rather dangerous to approach as every throb of his muscles release a harmful amount of radiation into his surroundings, which is why he takes extra precautions to reduce the radiation he releases by wearing chains that contain the radiation or regularly discharging it in safer ways. as a Montauk experimental, he knows Coven well and had accompanied them at certain points in their past.
Right now, he is Taketzu's renowned friend and partner. Neither of them ever tell how they met, but it is clear that they are very tight. They travelled to The Bastion together. Citadel was actually the one who told Taketzu about Coven, and was responsible for them meeting up.
Despite his brutish appearance, Citadel is a mostly gentle creature with a wise demeanour. He is often the voice of reason in contrast to Taketzu's rash words and actions. While the naga is an agility-based fighter, Citadel is the heavy bruiser, using an oddly-shaped club as a melee weapon and a strange apparatus to focus his nuclear powers into a ranged weapon. Though he's usually calm, he is known to get more aggressive if he doesn't release the energy he constantly produces. So be careful.