A nagual (na-GŪL) is not a beast. Nagualli are human magi who are born with the power to shift themselves into one or more animal forms. The most common form of a nagual is usually a large cat, such as a jaguar or puma, but talented nagualli can also transform into other animals. While mammal forms are the most common, birds are not unheard of, and it is theoretically possible for a nagual to turn into a cryptozoological creature, although to date there have been no credibly documented instances of this occurring.
Nagualli are accepted into the Magimundi community and have the same rights and privileges as any other person. That being said, there are those who consider nagualli to be “bestial demi-humans who only pretend to be people.” This bigotry was especially prevalent until the mid-nineteenth century, and has no place in modern magical sensibilities.
Despite mundane claims to the existence of such things as “conservation of matter,” when a nagual transforms into an animal, their size and age translates commensurately: a human will become an animal of a size and age proportionate to the life-cycle of that animal. For example, a large man is likely to become a large bear when he transforms; similarly, a young adult human will become a juvenile panther cub.
Nagualli are limited to one distinct animal shape per species when they shift. For example, a nagual who takes the shape of a wolfhound will be unable to take the shape of any other dog, or one with a bengal tiger shape will be unable to take the form of a siberian tiger. Likewise, the animal they turn into will have distinct markings which cannot be altered when they transform, nor can a nagual alter their human appearance through use of their shapeshifting.
Injuries or disabilities that a nagual sustains while human remain with them when they transform; a human with an injured arm would turn into a bird with an injured wing. The extent of the injuries are made proportional with the change, just like all other variables.
It is vanishingly rare for a nagual to be able to transform into more than two animals (aside from their base human form). There have always been rumors of the poly-nagual, who can transform into any animal, but such a being is more likely legend than reality.
Nagual inherit all the instincts of their specific animal when they transform, but not necessarily the skill to use them effectively. As with young animals, the mage must practice their abilities until they become proficient. While transformed, magi eat the usual diet of the animal they have become, and some even come to enjoy it. The quantity of the food in their stomachs will be transformed in terms of amount, but not in nature: a belly full of raw meat as a panther means a belly full of raw meat as a human.
When in their animal form, nagualli are sterile; they can perform mating functions with other animals, but will not produce any offspring. If a nagual is pregnant in her human form, the fetus is not represented in the nagual’s animal form and is completely unaffected by her time as the animal. A nagual in labor will be unable to shift into animal form until after she has given birth.
Nagualli retain their human intelligence while in animal form; however, the longer they stay in the animal form, the more likely they are to begin forgetting their humanity. There are cases of a nagual becoming trapped in their animal form permanently after having gone too long without taking their human shape.
Nagualli can be found in any Magimundi community. They are people. It is possible for a nagual to transform into an animal outside its native habitat.
When in the form of a person, a nagual is biologically identical to a person; when in animal form, they are biologically identical to that animal. When a nagual dies, it returns to human form.
Nagualli can eat whatever their animal forms can when in those forms. Food in the stomach of a human will be non-toxic to the nagual when in its animal form. So a nagual can eat a meal containing raisins and garlic and then shapeshift immediately into a canine with no ill effect.
An odd side effect of the shapeshifting process is that none of the products of the animal the nagual turns into (teeth, skin, claws, feathers, etc.) can be used for magical purposes. It’s almost as if magic itself considers that cheating.
As a remnant from the days of persecution, a spell had been developed to lock a shapeshifter into their present form for a brief time, which greatly assisted the Wizard-hunters of nagualli, but it is the opinion of this author that no good can come from the sharing of this spell. Naguals are human magi, and therefore the best defense is respect and courtesy.