Cygnia is a planet in the Hero Factory universe.
Cygnia was first mentioned by Corroder only in Comic 2: Core Crisis. There is little to no information regarding this planet although Corroder said that he had just as much fun there as he did on Penitentiary 1331. Considering he nearly destroyed the prison, we can assume that Cygnia suffered just as horrible a fate if not worse.
The idea of Corroder mentioning he was even on another world gives him far more character development than what was seen in the Hero Factory TV Show since this means he has taken up other destructive jobs on other worlds. Whether the attack on Cygnia was ordered by Von Nebula or not has not been revealed.