|“||One thing remains a certainty: At the height of their glory, even they could not have forseen their fate, nor the speed with which it was delivered.||„|
— Prof. Gerald Robotnik, "The Fourth Great Civilization" (Sonic Chronicles opening)
The Nocturnus Clan are a long-lost group of echidnas who appear as the major villains in Sonic Chronicles: The Dark Brotherhood. Archaeologists on Sonic's world referred to the ancient Nocturnus culture as the Fourth Great Civilization; GUN calls them the Marauders before their true identity is revealed. The leader of the Nocturnus Clan is Imperator Pir'Oth Ix.
Four thousand years before Sonic's time, the Nocturnus Clan fought a protracted war against their fellow echidnas, the Knuckles Clan, for supremacy in the ancient world. More technologically-orientated than Knuckles' ancestors, the Nocturnus prosecuted this conflict with professional armies and prototype Gizoids - ancient automata with a penchant for mimicry, of which Sonic Battle's Emerl was the most advanced to be created.
The war only ended when the Knuckles Clan was laid waste, not by the Nocturnus, but by Perfect Chaos after Chief Pachacamac assaulted the Emerald shrine - events recounted during Tikal's flashbacks in Sonic Adventure. With their rivals wiped from the face of the earth, the Nocturnus Clan "nearly colonised the whole world" (as attested by Shade in Chapter 6). However, their ascendancy was abruptly curtailed by the mysterious Argus Event, which saw the Nocturnus civilization (along with their capital city, the Nocturne) uprooted and imprisoned in the Twilight Cage.
When faced with the multitude of cosmic horrors cohabiting the prison dimension, the Nocturnus Clan was forced to change rapidly, from a clockwork-and-waterwheels tribal system to a sinister technophilic imperium. Through strategic alliances (or failing that, direct subjugation), Imperator Ix was able to dominate the other races of the Twilight Cage, and hatched a plan to return to Sonic's world with the power of the Master Emerald, leading to the events of Sonic Chronicles.
The troops of the Nocturnus army are Sonic's principal enemies during the second part of Sonic Chronicles. Clad in matte black armour and glowing sigils, their leech-blade attacks can sap friendly characters' health to replenish their own.
Although the Nocturnus Tribe have not appeared explicitly in any other Sonic media beyond the Chronicles game, they appear heavily reminiscant of one of the long-standing features from the Archie comics continuity: namely, the Dark Legion. Not just in terms of a similar name: like the Nocturnus "Dark Brotherhood", the Dark Legion were a faction of technophilic echidnas who fought against Knuckles' ancestors, only to be banished to the Twilight Zone, where time flows more slowly than on Sonic's world. Indeed, after the release of Sonic Chronicles, the Archie series began to make use of the name "Twilight Cage" (issue 205).
Pir'Oth Ix, the leader of the Nocturnus, has also been likened to Doctor Finitevus - a "Technomage" of the Dark Legion. Fans of the older UK Fleetway Sonic the Comic series, however, are quick to point out that Finitevus himself seems inspired by STC's Doctor Zachary. All three of these characters are evil-aligned, white-furred male echidnas, somewhat 'old', with a penchant for technology and megalomania.
The soldier classifications in the Nocturnus army are taken from Imperial Roman army ranks; triarius, hastatus, equite, and prateorian to name a few.