“The Fair Unknown” is episode eighteen of season two of Andromeda.
The Andromeda Ascendant is investigating a Calderan ship that has had its crew killed. On viewing the recordings made of the attack, a Vedran is seen on them. The Vedrans lived on Tarn Vedra (as did Dylan, although humans were more of a recent import), which has been cut off from the slipstream since the fall of the Systems Commonwealth. They are also the race who created the Commonwealth, and Tarn Vedra was the capital. None have been seen in over 300 years.
Dylan wants to find out what happened, so they head for a nearby world that the Vedran appears to have fled too, one that they apparently liked. It seems the Vedrans are deliberately absent from the remains of the Commonwealth. Quite what is going on isn’t known, but Vedran technology appears to have advanced since the fall. Perhaps they did not fall along with the rest of the Commonwealth.