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Julian Bashir is able to save the Dax symbiont, who is sent back to the Trill homeworld to be rejoined with a new host aboard the USS Destiny.

When the symbiont's health worsened, The Dax symbiont was implanted into a new host named Ezri Dax who was the assistant ship's counselor.

She was not trained to be a host but she was the only available unjoined Trill aboard.

Ezri had difficulty making the transition and sought out Ben Sisko on Earth.

She helped him on his mission and then returned to DS9 with him.

She accepts his request to stay on as station counselor.