Demons are almost always terrifying, but this is especially true in Demon Slayer. Their very existence is the primary reason the Demon Slayer Corps exists, and it's not an exaggeration to say these vile creatures are the biggest threat humankind faces in the series. They possess far too much strength for an ordinary person to handle, as well as regenerative abilities that make them hard to kill. Given enough humans to eat, these demons can even acquire supernatural powers.
The progenitor of demons, Kibutsuji Muzan, is so powerful that protagonist Kamado Tanjiro -- and the entire Demon Slayer Corps -- can barely keep up with him. Even worse, the villain isn't operating alone, with the Twelve Demon Moons working under him. Here's how that ranking works.
What Are the Twelve Demon Moons?
The Twelve Demon Moons are exactly what they seem to be: the top twelve strongest demons, whose powers are only second to Muzan himself. Given nearly every demon in Demon Slayer became what they are after receiving Muzan's blood one way or another, the Twelve Demon Moons were transformed the same way. However, the latter received a far greater amount of Muzan's blood, increasing their power by a staggering amount and amplifying their Blood Demon Arts.
The Twelve Demon Moons have three tasks. First, they had to search for the mythical Blue Spider lily, which Muzan believes will allow him to acquire a perfect immortal body devoid of any weakness. Second, they were to engage and slaughter the Demon Slayer Corps. Finally, they must serve him with utmost loyalty and offer themselves at a moment's notice.
How Are Muzan's Demons Ranked?
The Twelve Demon Moons are divided into two halves: the Upper-Rank and the Lower-Rank. Naturally, the Upper-Rank demons are leagues more powerful than their counterparts, and they seem to have a bone to pick with the Lower-Rank demons. Upper-Rank demons are powerful enough to fight and kill a Hashira, though the latter are strong enough to slaughter the Lower-Rank demons. An Upper-Rank is bad news for the heroes, especially if the Hashira is acting alone.
Both the Upper-Rank and Lower-Rank are further ranked from one to six, with one being the strongest and six being the weakest. Given the difference in strength, Muzan favors the Upper-Ranks more. He even exterminated the Lower-Rank demons later on -- except for one -- as he places great importance on usefulness and power. Likewise, only especially strong individuals can withstand consuming a huge amount of his blood without turning into ash.
Who Is the Strongest Demon Moon?
The strongest among the twelve is the one who holds the title of Upper-Rank One: Kokushibo, a former Demon Slayer named Tsugikuni Michikatsu. He was also the older twin brother of Yoriichi, the creator of the original Sun Breathing. His brother's genius caused a great deal of envy to Michikatsu, which only grew when Yoriichi lived to become an old man despite awakening his Demon Slayer Mark. That envy -- along with a fear of death after gaining his own Demon Slayer Marks -- resulted in Michikatsu accepting Muzan's offer to turn him into a demon.
Kokushibo's fighting prowess was second only to his boss. Despite turning into a demon, he was still able to fully utilize his Total Concentration Breathing and Demon Slayer Marks. He also had access to various demon abilities like increased strength, regeneration, flesh manipulation and more. Ultimately, three Hashira and a fairly strong Demon Slayer had to work together to eliminate him, and they didn't leave unscathed.
