Odo is the name of a shapeshifter on Star Trek: Deep Space 9, who doesn't know his origins or homeworld until around season 3. I guess the homeworld isn't revisited as a major plot point until season 6? I don't remember...seasons 6 and 7 were honestly kind of a blur for me.
I think prior to season 6, the Klingons and Romulans tried to destroy the Dominion by taking out Odo's homeworld in a sneak attack. Odo's people turned out to be the rulers of a large empire that sought to conquer solids (non-shapeshifters).
Full disclosure: I still don't.