Hunters (ハンターHantā) are a new addition to the Madoka Magica Universe introduced in Puella Magi Madoka Magica: Rebirth, specifically within the Rebirth Story Arc. Hunters are the twin companions to the Puella Magi, assisting them in combating witches and the new threat of the archfiends as well as secretly serving a secondary purpose known only to the Incubators. Hunters used to be wide-spread around the world until the Hunter/Magi War, which also gave rise to the Hunter Virus, wiping the world clean of their kind, and leaving the Magi alone just as often as the Hunters themselves had found themselves "alone".
Despite the near eradication of the Hunter species hundreds of years ago, the species lived on in secret, contained to tiny pockets and thin, unexpected strains of the Hunter Gene being passed down from father to son, weakened by the Hunter Virus, but still able to awaken.