In every supernatural and fantasy anime a wizard or a mage has this powerful ability to call certain supernatural entities to assist them wither in a battle or some sort of for some other reason. They help them fight against the enemies. Some of those very common creatures that we have seen with withes or wizard are black cat, an owl or a raven. It’s kind of a fundamental thing in a magical anime especially for girls where they ae accompanied by some cute animals that everyone wants to hug and kiss. While in some anime these entities are humans with supernatural powers that suits the wizard who summon them.