At the beginning of the series, Jadzia has just recently been joined with the symbiont Dax after the natural death of the previous host, Curzon Dax. Curzon had been a friend and mentor to station Commander Benjamin Sisko, and as Jadzia Dax, they continue this friendship despite the change in circumstances. Throughout the series, Sisko refers to Jadzia Dax by the affectionate nickname "Old Man". She begins the series at the rank of lieutenant; at the start of the fourth season, she becomes a lieutenant commander and remains one until her death in the sixth-season finale.