The Xindi are six sentient species that evolved in parallel on the planet Xindus in the Delphic Expanse. After a global conflict that destroyed their homeworld in the 2030s, the Xindi-Avians became extinct. The remaining five species – Xindi-Aquatic, Xindi-Arboreal, Xindi-Insectoid, Xindi-Primate, and Xindi-Reptilian – fled the ruins of Xindus and formed a Council to guide their fellow survivors in finding a new homeworld.
They were the main antagonists in Season Three of Enterprise, having been tricked into attacking Earth. The conflict won’t be recounted here, but they seem to have reached a detente with Earth through the actions of Captain Archer and the Enterprise. Little is known of what happened with the Xindi thereafter, except that they joined the Federation at some point between the Enterprise Era and the 28th century. Thus, they may make interesting antagonists or allies for the TOS or TNG Eras, giving GMs free reign over when they joined the United Federation of Planets.
The five surviving species of Xindi are presented as playable races in the PDF below. The Xindi-Insectoids and the Xindi-Reptilians are the most likely antagonists, so Minor NPC stats have been presented for the two races.
Click the images below for the combined PDF of the five Xindi species, and the PDF for the Xindi-Insectoid and Xindi-Reptilian NPCs.