Werebeasts

Werewolves are but one of several does types of therians, aka werebeasts, lycanthropes, shifters, beastfolk, or whatever you want to call them. Therians are those with both a human spirit and an animal spirit within the same soul. It's... really weird, because it's like having two different versions of one's self--both equally true and accurate, but they are not always in agreement. They have different instincts, morals, senses, and even appearances, as the animal spirit wants to appear like the animal it is, and the human thinks bipedialism and opposible thumbs are pretty damn important. So, the trick with most therians is to learn how to reach a harmony between these two spirits, and bring peace to their soul. A therian with this is in complete control of themselves, and can access the primal power of the beast and the wisdom and intelligence of mankind at the same time.

This dual-spirited nature also gives therians access to spiritual powers not entirely unlike the other inhabitants of the Spirit World. This includes the ability to travel between the mortal world and the spirit world, enhancements to their natural abilities, the ability to peer through space or time, rapid healing, and so on and so forth. With their two spirits, a therian is almost bursting with anima, granting them a lot supernatural powers. Their ability to walk with one foot in the world of spirits, and one in the world of mortals is what has lead to the various therians becoming the guardians of the Spirit World becoming guardians of the Axis Mundi.

Now, most therians are born into families where the gift of shifting has been passed down for generations. However, not all therians are born--some are made. Sometimes, a shaman or a medium will conduct a ritual that invites a beast spirit into their body, willing becoming therians. Sometimes, it will be a curse, cast by a mage or a powerful spirit, transforming a human into a beast. And other times, it is the accidental result of a therian injuring a mortal, and that mortal drawing some of the therian's anima into themselves. Usually, this does nothing more than cause the wound to heal quickly into an ugly scar. However, on occasion, this anima will be taken into the wounded's soul, and, well, it will call in a beast spirit.

And that's where you get the whole "rabid werewolf transforming an entire town" myth from. See, an infected therian has no idea what the hell is going on in most cases, and thus its spirits are wildly out of sync--usually they are entirely human, but during times of spiritual power--such as under the full moon--the beast spirit will be in control, and that spirit has no humanity, or anything else holding it back. This infection can of course be cured by removing the beast spirit from the soul, but that could damage the soul, and as should have been established under the undead section, damaging a soul is bad. Usually the safer bet is to get a therian to teach the new werebeast how to handle their new nature so that they are no longer a danger to themselves or others.

Besides werewolves, there are dozens of other therian lineages, from neizumi to nagual to bultungin to kitsune to weretigers to tengu. As mentioned, there's several dozen different strains of lycanthropy--most of them are carnivorous mammals, but there are the occasional avian or reptilian clan among them.