Kyubey is the main antagonist in the anime and manga series Puella Magi MadokaMagica, and had some minor roles in its spin-off mangas Kazumi Magica and Oriko Magica. He appeared as the "Messenger of Magic" who would grant wishes to girls. However, in return they sign a contract, and serve as a Puella Magi (Magical Girl). Their job was to kill Witches, creatures that fed on the hopes or dreams of ordinary people. However, this is actually just a distraction from Kyubey's true goal.
Kyubey is an Incubator/Messenger of Magic. Because of this, he, like his race, cannot exhibit emotions of any kind. As a result, Kyubey often appears cold, calculating and scheming; traits that make him appear villainous in the series. Kyubey, however, only seeks to achieve a goal; to preserve the universe from entropy. To meet this goal, he takes all means logically efficient and reasonable; namely creating Puella Magi.