can you show a screenshot? it might be for the leebrans

I'm certain the Centesians are an ancient species that existed long ago, hence why you find their structures. The Avakin have some Centesian tech in a few of their unique weapons, but I'm not sure if the Centesians will ever be added as a race. Could be wrong, of course.

Centesians are planned down the line to be playable.

Bullseye55 and Surfer are both correct here, the Centens are planned as a playable race for a future update! The Centens are an ancient race that existed long ago (and are now considered largely extinct), but you'll be able to play as one of the few remaining Centens in a future update.

To see the Cent race as playable would be a good change of things.