Inhumans are a multi-ethnic and multi-racial fictional species in the Marvel Universe. They have several societies including Orollan, Utolan, Attilan, and more through out the Galaxy.
They were created by Jack Kirby as an allegory of people from another culture with a scientific/religious ritual called Terrigenisis whose culture and traditions are tested when they make contact with the human world after being hidden for millennia due to human and Kree persecution.
Attilan was one inhumans' tribe's safe havens. Their popularity comes from how this tribe's monarchy interacted with super beings of the Marvel Universe and how their society changed along the way.
Despite being a species of thousands of multi-ethnic fictional characters, their passed storylines that tackled the issue of slavery has been misinterpreted as a promotion of it.