Plutonia is a member of the Imperial Guard, a multi-ethnic group of super-powered alien beings who act as enforcers of the laws of the Shi'ar Empire. Part of the division of the Imperial Guard known as the Superguardians, the enigmatic Plutonia was one member of the injection team that attacked were sent to attack the X-Men on the orders of their Empress Lilandra, who was at the time under the mental control of Charles Xavier's mutant twin sister Cassandra Nova.
Prior to the battle, Plutonia set off to investigate an alarm signal that was being broadcast across the Imperial broadband wavelength. She discovered her fellow Guardsman and lover, Smasher, who had been sent to Earth by Lilandra prior to her possession to warn the X-Men of Nova's actions. She returned with Smasher to the X-Men's headquarters in the Xavier Institute just in time to convince the Guard's praetor, Gladiator, of the true threat. Together, the Guard and the X-Men managed to defeat Nova and free Lilandra.