From Sonic Retro
Argus is the name given by the Nocturnus to the hypothetical entity which may be responsible for sealing them (and many other races) inside the Twilight Cage. The name comes from a strange "mental sound" which the echidnas heard moments after being whisked away from their world - a noise which sounded like "Argus".
Whether "Argus" is an actual entity; who, or what, it is; and its reasons for imprisoning species in the Twilight Cage (occurrences called Argus Events), are completely unknown. On deciphering Precursor tablets, Nestor the Wise reveals that the ancient civilizations of the Cage believed Argus to be some sort of supernatural being, that was imprisoning races who became too powerful or otherwise dangerous. As of the end of Sonic Chronicles: The Dark Brotherhood, the validity of this hypothesis remains unconfirmed.
|Sonic Chronicles: The Dark Brotherhood|