Marius St. Croix grew up living a pampered life with his family in the small European principality of Monaco. When his mutant nature manifested, Marius’ mother became the first victim of his need to feed on genetic material to survive. Seeking more power, Marius studied dark magic, eventually inviting his sister Monet to join him in his efforts to rule the world. After she scornfully rejected him, an irate Marius magically trapped her in the form of a red-skinned mute creature dubbed “Penance.” Believing he had killed Monet, Marius’ younger twin sisters used their own powers to banish him to another dimension, but were unable to prevent Penance from following him. After years of imprisonment, Marius—now calling himself Emplate—eventually learned to traverse the dimensional barrier and returned to Earth, where he employed the dwarven D.O.A. as a manservant.
Learning of the powerful mutant Chamber, Emplate intercepted him upon his arrival in the U.S., but was driven off by the Generation X students. Among their number were Marius’ younger sisters, who had used their powers to merge into M, a single being resembling Monet. After Penance escaped and joined Generation X, Emplate sought to recapture her and so enslaved several mutants, as well as Chamber’s former girlfriend, Lady Gayle Edgerton. Emplate and his “Hellions” attacked and captured Generation X, but were defeated thanks to the X-Man Bishop, who noted that hordes of Emplate-like creatures existed in his future time. Before his defeat, Emplate enslaved Generation X member Synch and sent him to attack his own family; however, Synch ultimately fought off Emplate’s influence. Later, Emplate and the twins were temporarily fused into a new being named M-Plate, who allied with the superhuman bounty hunter Chimera in an attempt to gain control of the Universal Amalgamator, a device that could merge all sentient beings in the universe into a single consciousness. Their plan was thwarted by Generation X, and Emplate and the twins were all separated by the mutant Dirt Nap. While merged with their brother, the twins learned of Monet’s true fate, and subsequently used their powers to merge with Penance and free her, becoming Penance in her stead.
A weakened Emplate later returned and attacked Generation X, but was defeated by a massive explosion generated by Jubilee which also forced the twins out of their Penance form, creating a third Penance whose identity remains unknown but is suspected of being related to the St. Croix siblings. Emplate was subsequently held within the Academy’s infirmary until the school was all but destroyed during a riot, during which Emplate presumably escaped.