See also: Apostolos (COUNTER/weight Wikia). Potential COUNTER/weight spoilers at link.
Apostolos is the planet the human-offshoot Apostolosians come from. Tens of thousands of years ago, it was the seat of an empire.
Apostolosians look like humans, but they have gills on their necks surrounded by visible scales that continue up the sides of their faces. They may have other fish-like features as well.