Regenerator

A Regenerator (再生者リジェネレーター) is a human powered up with bio- or nanotechnology to be given the ability to heal wounds inflicted on average humans.

Regenerators are described as the peak and crystallization of anti-monster technology. Regenerators are described as a "man who transcends the human race in order to fight demons", meaning that they were specifically made to fight supernatural creatures like vampires and ghouls.

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Technically aren't humans, they still count as one because of the fact that they possess the same willpower as a normal being and generally, acts and behave like a person that can fit into society; unlike vampires. It is also unknown how this technology or invented, along with how many Regenerators are there; or, only Section XIII possesses this technology. Yet, they're simply explained to be a technique humanity developed specifically for fighting vampires without having to try, for the most part that is.

While they're also technically human, they displayed inhumane ability which can be considered "unnatural", aside from regeneration. With a physical strength far more stronger than average humans like Integra. Alexander Anderson, the original Regenerator, displayed physical capabilities superior than an average Artificial Vampires.

Their willpower and determination however, stays the same and Anderson displayed it perfectly; previously, Alucard thought that he was just a monster, however, after displaying much determination into defeating him, which was comparable to the former vampire hunters in the 18s, Alucard's thoughts about Anderson seemingly changed.

The only known Regenerator throughout the series was Alexander Anderson; however, it is possible that after his death, Heinkel Wulf replaced him as the trump card of Iscariot and was possibly made to be a Regenerator as well.