Basara

A Basara (婆娑羅バサラ) is an evolved and a humanoid Impurity that has absorbed the powers from Exorcists by killing them. When they absorbed enough, they turn into a Basara regaining a human form and the human speech. Their ranking is based of their time of birth. The smaller the number, the older and stronger they are. There are eleven (eighteen in the anime) Basara known, and each is powerful enough to challenge a Guardian and kill a mass of Impurities.

Appearance
It is because they are born from people's sins and karma, that is why Impurities look a lot like humans when they evolve into Basaras, but they still retain characteristics that distinguish them from humans. Unlike humans : They have kuji-kiri on their torsos and one eye of a normal human, while the other is black, with a red pupil, and have cracks around it. Basara can be recognized by their extremely dark skin. Some Basara tend to absorb spell power by killing Impurities. If a Basara absorbs much more power, the Basara becomes more human in appearance as demonstrated by Kuranashi when he removed his mask, revealing his face with both normal eyes of a human. Hijirimaru also have a pair of normal eyes in his second form after he consumed Higano's spell power when he died. The only thing that retain their characteristic as Impurities or Basaras is their Kuji-kiri marks even if they gain so many spell power.

Human Speech
After turning into a Basara they regain the human language and are able to use it without problems. They will communicate with other Basara to plan something or with Exorcists to make them feel more despair or ridicule them.

Enchanted Gear
Due to the absorbing from the different powers from the Exorcists they are able to use the Enchanted Gears as well, by using the curse talisman.

Regeneration
Basaras such as Kamui seem to be able to regenerate their body parts after getting severed or damaged.

Immense Strength
Different Basaras have shown on numerous occasions to possess a high degree of strength. When battling exorcists, they are able to defend themselves by hitting their opponents without putting much effort into it.

Enhanced Reflexes
Basaras, such as Chijiwa and Momochi, had proven themselves to be able to dodge from their opponents' attack.

The Strongest Ones
The oldest ones just only mean they are the strongest of all. The strongest three Basaras are Kuranashi, Chinu and Ashiya Doman. They were born since the birth of Magano 1000 years ago.