In 2153, the Xindi attacked Earth with a deadly probe, cutting a swath from Florida to Venezuela and killing 7 million — all because of false information fed them by the Guardians, one faction in the Temporal Cold War. The small-scale test was to be followed by a larger weapon to destroy the planet entirely — all to pre-empt what the Xindi are told will be an Earth attack on their own planet in 400 years. That "news" is in fact, however, a lie by the Guardians to further their position in the war, and is finally realized by a majority of the Xindi in time to barely avoid the attack.
There are five distinct species of Xindi: Xindi-Primate (initially called "Xindi-Humanoid"), Xindi-Reptilian, Xindi-Arboreal (sometimes called "Xindi-Sloth"), Xindi-Aquatic and Xindi-Insectoid. A sixth species, the Xindi-Avians, are now extinct: they were killed off in a war that went on for nearly a hundred years, destroying Xindus and spreading the other species to nearby habitable planets. In the mid-22nd century the Xindi Council was formed to reunify the surviving races, but their attention was diverted from a peaceful agenda to an aggressive one in order to address the alleged "human threat." Despite their varied forms and typical mistrust, they all share a common physicality: a short vent-like opening in the "cheek."