The weretigers are one of a number of types of lycanthropes, humans inflicted with a supernatural virus which allows them to take the the power and appearance of a specific species of animal, in this case, tiger.
Tiger lycanthropy is one of the harder-to-catch strains, and the weretiger culture sees attacking outsiders as an abomination. Being given tiger lycanthropy is seen as a reward for a job well done, and they think it is a sin to give it to someone not worthy. It is also one of the few forms of lycanthropy that can be inherited, as well as caught. Consequently the weretiger culture is strongly divided into pureblood clan tigers, who are inherited lycanthropes, and attacked ones, whose coloring matches natural tigers. However, according to the Mother of All Darkness, all of the clans started off as survivors of attacks, and have just forgotten this because the power breeds true. It is hinted that the Yellow Clan might still possess this power of spreading all strains of tiger lycanthropy, which could explain why Anita caught all of them, although there are too few recorded survivors of yellow tiger attacks to draw any conclusions.
Tigers tend not to announce they are infected, and entire families may stay in "the closet" for generations. Intermarriage is common in order to keep the bloodlines pure, and forced marriages between clan members aren't unheard of. Most weretigers have arranged marriages, and they have been known to abduct known tigers if an arranged marriage cannot be done. There used to be only four known clans of tigers within the United States, and they all kept mostly to themselves, although as the series proceeds we meet tigers from all five clans.
They are a matriarchal society (led by a woman/queen), unlike most of the other lycanthrope societies which are patriarchal (led by a male/king).
At one point in their history all weretiger clans were found in China and were ruled by the Queen of the Yellow Clan, and through her by the Father of the Tigers. Marmee Noir killed the last known High Queen of the Yellow Clan and weakened the powers of the Father of the Tigers, permitting her to defeat him and steal his powers. The Mother of Darkness then influenced the First Emperor of China to hunt down the weretiger clans, forcing them into exile.
She permitted her servants, the Harlequin, to keep their yellow tigers as their animal to call, but continued to hunt the Yellow Clan to extinction. Secretly some of the Harlequin spared some of the yellow tigers and hid them from Marmee Noir, breeding the bloodline until the day they can put the Darkness back to sleep. Because of all of this, it's no surprise that there aren't more known survivors of a yellow tiger attack.
After over two thousand years, some of the clans settled in the New World, including the White and Red Clans. The Blue and Black clans have dwindled to only a few individuals, while the yellow was believed extinct.
There's an ancient weretiger prophecy that says the next vampire that can control weretigers will kill the Father of the Tigers and the Mother of All Darkness. Because by vampire customs everything a human servant accomplishes is counted as being done by the vampire master, Anita killing those two ancient vampires counts as fulfilling the prophecy, or at least that part of it. The rest of the prophecy is less clear, but implies that if the tiger isn't married to the king and queen, whatever that means, the Mother of All Darkness might find a way back.
The metaphysical community has interpreted the prophecy to mean that to be on the safe side at least one tiger must be included in the commitment ceremony Anita, Micah and Nathaniel are planning to have after Anita marries Jean-Claude. At the end of Dead Ice it looks like Dev might become that tiger if his inclusion in their poly group continues to go well, although it's still unclear whether Micah's own new tiger form would be enough.
- The 'call' is the ability of dominant tigresses to attract lovers and eventually mate. The stronger the weretigers power the larger the distance a call can travel. Only the strongest dominant queens are able to block another queen's 'call'.
- Heightened hearing, agility and endurance; they are significantly stronger and faster then normal humans.
- While regular weapons can cause them injury, they will heal most wounds given time, but are still vulnerable to silver
- Weretigers can give their beast to another tiger avoiding transformation. This allows females to carry a pregnancy to term. Though because of the tigers they have taught different lycanthropes species like wolf and leopard to keep the fetus through out the the pregnancy
While the weretigers were ruled by the Master of Tigers they were more powerful and had special abilities specific to each clan.
- The Black Clan had the power to control water.
- The Blue Clan could control air. They could raise storms and make them obey their will.
- The Yellow Clan could control the earth and all energies upon it, and were capable of provoking earthquakes.
- The Red Clan had the power of pyrokinesis. Alex Pinn awakens this power after sleeping with Anita.
- The White Clan could create electricity.
Once there were hundreds of weretiger clans, one for each colour the tigers could have, but most have gone extinct or have simple dwindled to only one individual. Some of this include:
- Black Clan - the last surviving members are Domino, Sebastian and Yiyú.
- Blue Clan - some of the last surviving members are Cynric and Fortune.
- Yellow Clan
- Chiang - Queen of a Clan.
- Li Da - Tiger prince of the Red Clan.