Every fantasy setting has its varied and strange collection of creatures, animals and monsters that come from all manner of myths and legends. Most come down to three different types of creature: those that are created created and bound by magical means; those that were adjusted through sorcery; and those that are of the natural world. The question however is what defines a creature as being one of these three types - is a Ogre a magical creature? Is a Dragon?
When thinking about these kinds of beasts, the very way in which their existence happens is through magical means or cannot live without some element of magic involved. An example of this could be Dragons. While they are really large lizards(perhaps an evolved version of the Draco Lizard of Indonesia) there is almost no way that they could fly and breath fire the way they do without some kind of magical power letting them do so. Unicorns, vampires and even Fae creatures are also quite likely to be magically reliant, as their power flows through their blood and grants them their unique, albeit terrifyng gifts.
A person or beast that was once ordinary and was transformed through the power of magic. There are two ways of looking at these fantastical beings - as cursed, or as experiments. Cursed creatures such as the minatours were made as punishments, by people who wante to exact revenge on their hated foe for their lifetime. As experiments, they could be a combination of creatures that have been able to exist, procreate and propogate in the world, becoming a natural species with magical origins - similar to Owlbears.
Lions, tigers and bears… goblins, orcs and ogres. This is all about the creatures that have evolved naturally across the world, developed intelligence to some degree or rely on their instincts for survival. Anything from mundane animals such as wolves and hyenas are definately part of this, but also humanoid species like kobolds and giants - races that have no magical link to existing but are still fantastical in their own rights.