Dark Mobius is a major antagonistic force in the Sonic: Cosmic Crusade multiverse and is a dystopian version of Mobius located in an alternate-universe, within this reality Mobius has taken the role of an aggressor and conquered nearly all of their native reality and become a serious threat to the mainstream multiverse as it seeks to expand out and conquer mainstream reality.
Dark Mobius is noted as an embodiment of lawful evil, just as Evil Mobius is an embodiment of chaotic evil - as such residents of Dark Mobius are fascist warlords who follow strict rules and xenophobic codes, seeking to expand and either enslave or wipe out all other species : it is worth noting this extreme level of corruption seems to only be seen in Mobians of the Dark Mobian universe, other species in Dark Mobius seem to act much as they do in the mainstream world, being either peaceful or neutral and often suffering greatly as a result under the oppressive rule of the Mobian Empire.
By its very design Dark Mobius is an enemy to all other factions in the Cosmic Crusade multiverse, even the Bane Empire stands against the Mobian Empire - mostly because neither faction can tolerate the existence of another faction that may rival them in influence and power.
Whenever Dark Mobius invades the mainstream multiverse it causes considerable conflict, especially on Mobius, since facing off against the Mobian Empire reminds many of Mobius' heroes how easily they could become a threat just as bad as Bane or Robotnik - the act of facing such brutal and sadistic versions of themselves and loved ones also has a heavy psychological tax, even on veteran members of the Cosmic Crusade.
Worse still is the fact Dark Mobius plays on the resentment, fear and frustration many Mobians have in relation to other planets, who some Mobians blame for bringing Bane to Mobius and allowing Robotnik to return to power - while most mainstream Mobians try and suppress these emotions Dark Mobius is an insidious enemy and knows how to fan the flames of doubt and distrust so as to turn many Mobians towards their way of thinking : a danger Sally has tackled numerous times as she tries to keep Mobius allied with the rest of the multiverse in defiance of attempts by its enemies to see said alliances crumble and thus weaken Mobius, allowing it to be captured once and for all.
- Dark Mobius has a near-identical flag to Mobius Prime (mainstrema Mobius) - the key differences are that it is both slightly darker in coloration and has a prominent sword symbol over the Acorn Crest, which symbolise the warlike nature of the Mobius Empire versus teh more peace-seeking nature of the Acorn Legacy.