From Warhammer 40k - Lexicanum
The Nagi are a xenos race from the world of Sha'galudd. Highly intelligent worm-like creatures, the small Nagi are known for their mind control abities. When they were first discovered by the Tau Empire, they were despised by the Tau, who fought a series of violent conflicts with them. However they have since agreed to a peace accord and have joined the Tau Empire. Nagi frequently serve as advisors to the Ethereal Caste.
- 1: Codex: Tau Empire (6th Edition), pg. 34