Shapeshifters are supernatural versions of several species of normal animal, born with the ability to assume a human form.
Shapeshifters are intelligent (as in human-level intelligent), and can learn human languages and customs. How inclined they might be to follow those customs, however, is likely a matter of personal preference. They can also learn the ways of magic.
Despite their ability to learn human customs, shapeshifters' animal upbringings endow them with all the instincts - and the resulting unpredictability - of an animal of their species.
Contrary to the legends of such creatures as werewolves, shapeshifters' transformations are not governed by the lunar cycle. However, they are quite vulnerable to silver.
In their human form, shapeshifters retain some vestige of their animal nature, making them easy to spot if you know what to look for.
There are several varieties of shapeshifter:
Bear - Found throughout the northern hemisphere, and rarely display magical ability. Their animal vestige consist of extensive body hair
Eagle - Found throughout Europe and North America, eagle shifters commonly use magic and are especially good at dealing with sky spirits. In human form, they have sharp features and dark eyes.
Fox - Mostly found in Japan and China, and commonly use magical skills, favoring illusion and manipulation spells. Their easy-to-spot vestige is a long fox tail.
Tiger - Found in Asia, the rarely display magical ability. They have cat-like and/or reflective eyes in human form.
Seal - Found worldwide, in coastal waters. Commonly display magical ability. Have webbed toes and sometimes fingers in human form.
Warek - A leopard shifter found in Western Africa, they're the most common shifters on the continent. They have bad reactions to gold rather than silver.
Wolf - Possibly the most famous shifter type due to the legends of the werewolf. They're found throughout the northern hemisphere, and magic ability is uncommon. Display hairy palms and eyebrows that meet in the middle in their human form.