Demon

Demons are carnivorous, vampire-like creatures whose food is human flesh. They are nocturnal, since sunlight is lethal to them, yet they do not sleep and so remain awake through the day. Their bodies are extraordinarily tough and heal almost any injury at once, even regrowing a severed head, which leaves ordinary weapons useless against them. Only a Nichirin Sword, forged from sunlight-absorbing ore, can deal a fatal wound, and even then decapitation is the surest way to kill one. They also despise wisteria, a flower whose scent repels them and whose extract is poison to them.

Nearly every demon is driven to hunt and devour people, and most lose the memories of their former lives, keeping only a darkened version of their old personality. A handful, such as Nezuko Kamado, Tamayo, and Yushiro, hold on to their human feelings. As they eat more humans they grow stronger and can develop a Blood Demon Art, a power unique to each individual. Rarer human blood types nourish them more, and the rarest of all, called Marechi, is worth roughly a hundred ordinary humans in a single meal.

The Demon Slayer Corps is the demons' chief enemy, an order honed over centuries to wipe them out. Because of this, demons live in hiding and the public stays largely unaware of them. Some, like Muzan himself, slip into human society both to escape hunters and to feed more easily. Most demons prefer to work alone and are fiercely territorial, fighting one another over prey and hunting grounds, since Muzan forbids them from gathering in numbers. The Spider Family, held together by Rui with Muzan's blessing, is a notable exception.

Every demon is tied to its progenitor, Muzan, and pledges obedience to him through fear and manipulation. His control is not absolute. A demon of unusually strong will can sometimes cut the bond, becoming immune to his curse and nearly invisible to him. Because his cells run through all of them, his death means the end of every demon he made.

Muzan Kibutsuji is the first demon and the source of all others, having transformed when an experimental medicine built around the Blue Spider Lily saved him from a fatal illness. His most powerful servants are the Twelve Kizuki, among them Upper Rank members such as Kokushibo, Akaza, Doma, Gyokko, and Hantengu. A rare few stand apart from his rule: Nezuko Kamado, who reverts to human after the final battle, along with Tamayo, Yushiro, and the cat-turned-demon Chachamaru.