The Nocturnus Clan, also known as the Nocturnus, the Nocturnus Tribe, the Marauders, the Fourth Great Civilization, and the Dark Brotherhood are a rival clan/race of the Echindas who used to be from Sonic's world 4,000 years ago but in their moment of triumph, a dark force wrenched them from their home and into the Twilight Cage. They are the titular main antagonists of Sonic Chronicles: The Dark Brotherhood and they are led by their leader named Imperator Pir'Oth Ix.
The technology they use to do battle with is very advanced. So advanced they even have Gizoids, which they created anyway. When they attack, they can usually take some of your HP away from you.
The Nocturnus Clan is a highly advanced in terms of intelligence civilization and is known to have caused several world-breaking achievements in the ancient world. Even by today's standards, the Nocturnus Clan's technology is dominant over anything else in the world. And therefore during the time they resided on earth, they were highly dominant. They are seen as an evil alter-ego to their rivals, The Knuckles Clan.