During the Mutant Massacre the Morlocks were thought to have been completely slaughtered but a the last minute Mikhail Rasputin transported many of the Morlocks to another dimension known as The HIll. In this dimension time moves faster than ours and during the time between the Mutant Massacre and Sack's first appearance, 10-20 years is thought to have passed. In this dimension the Morlocks are forced to constantly fight their way up a giant hill to reach Mikhail's fortress at the top. Reaching the fortress means that you are one of the strong and you are allowed sanctuary in the fortress as one of Mikhail's chosen.
Mayor Story Arcs
The group Gene Nation, originated from this chosen group of mutants. Sack is a founding member of Gene Nation and he first appeared in " Uncanny X-Men" #323 (August, 1995). Sack and another member of Gene Nation, Vessel, appeared on the anniversary of the mutant massacre vowing to take a hundred human lives for every mutant life that was lost during that event. Sack killed a county coroner and another civilian. The X-Men arrived and after a short fight they fled. The X-Men track down the members of Gene Nation and confront them about their attacks on innocent civilians. After another fight Callisto takes Gene Nation, Sack included back to the Hill.
During the events of Storm's limited series, she is transported to the Hill where she fights her way to the top and enters Mikhail's fortress. She finds that Sack, now going by the name Glass is one of Mikhail's chosen. Storm beats Mikhail and takes all of the Hill's residents back to the real world and allows them to settle in a remote village in Africa.
Sack is absent from the next two incarnations of Gene Nation and is next seen as a resident on the front lawn of the Xavier Institute as a member of the 198 after the events of M-Day. He is one of the mutants who volunteers to be implanted with what is described as a harmless tracking chip by the O.N.E. It is soon found out that the chip actually allows the Office of National Emergency to control and regulate the actions of mutants who have had it implanted and Mr. M removes it from Sack and everyone else who had it implanted.
Following mutantkind's exodus from San Francisco to their new home on Utopia, Sack attempted to take control of a portion of the island by taking several of the younger X-Men hostage. Unfortunately for him, his efforts at blackmail were stopped by Psylocke and Dazzler, who assisted Surge's team in freeing their comrades and defeating the gelatinous villain.
Sack is among the mutants who are made X-Men by Cyclops to help taking part and fighting against the Nimrod invasion. He and a group of others were prepared to jump in and fight when Toad tried talking them out of it, pointing his finger at Sack. At the very moment that Sack tried to shame Toad for his cowardice, a Nimrod descended; taking off Toad's finger, firing at Sack & decapitating him. Sack's head fell to the floor. Any hope of his survival was lost when a second Nimrod landed on Sack's head, crushing his skull.
Powers and Abilities
His body is mostly consisting of blue ectoplasm, essentially giving him the form of a ghost. His ectoplasm is covered by pliable and transparent skin. Bullets pass though him with no effect. He has been wounded by energy attacks but has regenerated at rapid paces, giving him a healing factor.
He can meld himself to a human body and take possession of its functions. The process is lethal to his hosts. Sack can search for a new host body as soon as his current one dies. He can not control more than one body at the same time.