Incubator

SPOILER WARNING!! An Incubator is a cat-like alien creature who grant wishes for Magical Girls in exchange for them fighting Witches and other creatures. Incubators are incapable of feeling emotions and this prevents them from feeling guilt when deceiving Magical Girls into making wishes with them. They make these wishes so that way a Magical Girls can kill Witches, and once they use too much magic or succumb to despair, turn into Witches so they can release energy. This energy is what Kyubey and other Incubators use to preserve the Entropy that sustains the universe.