Dax is a xenomorphic character in the fictional Star Trek universe. The Dax life form is a symbiont—one that lives inside & bonds to Trill humanoid hosts. The first appearance of a Trill was in the episode "The Host" from the fourth season of Star Trek: The Next Generation; in that early version, the personality of the being was entirely that of Odan, the symbiont within the host, whereas the personalities of the Trills in Star Trek: Deep Space Nine are a blending of the symbiont Dax and its sequential Trill hosts. Two of Dax's hosts, Jadzia Dax and Ezri Dax, appear as major characters in Star Trek: Deep Space Nine. Others are only seen in flashbacks and when taking over others' bodies in the DS9 season 3 episode "Facets". Dax's hosts also appear in spin-offs such as Star Trek: The Human F