Hollow (formerly called Penance) is a character associated with the St. Croix family who first appeared in Generation X #1 (November, 1994), and was created by Scott Lobdell and Chris Bachalo.

Hollow also possesses animalistic agility, as she usually moves around by crouching and padding and leaping on all fours; she has been shown on occasion to use her feet to grab and grip objects and people.

The original creative team behind Generation X, Scott Lobdell and Chris Bachalo, intended Penance to be a girl called Yvette from Yugoslavia.

The twins convince Gateway to teleport them, Husk, Skin, and Emma Frost to the airport, where Emplate has already managed to absorb the powers of Chamber and Banshee.

The twins immediately display both a detailed knowledge of Penance's plight (specifically her connection to her former captor, Emplate) far beyond even her teachers,[16] as well as a curious reluctance to physically engage the girl.

While the rest of the team scrambles to try and capture Penance by force, Chamber merely lets her come to him, sensing that their mutant powers have made them both monsters and kindred spirits.

[17] The team soon becomes aware of Monet's reoccurring, temporary trances, where she "spaces out" and is typically unresponsive for several minutes at the least (due to Claudette's autism).

An early occurrence of this trance state forces Synch, Skin, and Jubilee to abandon her during a trip to New York City, where they end up battling and defeating Hemingway of Gene Nation.

[21] During the Generation X Annual '95, the team is introduced to Cordelia Frost, Emma's younger and even less trustworthy sister, and her constant companion, the mutant Mondo, who is able to absorb both organic and inorganic matter, taking on its properties, as well as transport himself through these same materials.

This time, Emplate has recruited a team of Hellions to do his dirty work—all of whom are under his thrall, including Gayle Edgerton, Chamber's former lover who was paralyzed when his powers first manifested.

[27] While the rest of the Marvel Universe was occupied with Onslaught, Emma, sensing the disturbance, tried to protect Generation X by taking over their minds, gently but firmly forcing them to accompany her to her home.

[30] Though Sean and Emma discuss treatment options and try to talk Monet into seeing a doctor, she abruptly destroys the school's cars on the scheduled date and refuses to go.

However, Monet was the most devastated when Synch sacrificed his own life to stop an exploding bomb that had been placed in the academy by Emma Frost's sister, Adrienne.

[volume & issue needed] After Generation X disbanded, M temporarily joined Banshee's militant X-Corps with Husk and Jubilee to keep an eye on the devastated Irish mutant.

However, the X-Corps were soon destroyed by Mystique, leaving M to join the X-Corporation's European branch, located in Paris, where she assisted Cannonball, Multiple Man, and Siryn in defeating Weapon XII.

[volume & issue needed] Following the events of House of M and the shutdown of X-Corporation, M, who also has appeared on the cover of Vanity Fair,[42] has opted to join X-Factor Investigations, a private detective agency run by Multiple Man.

Monet completed her first mission on the team by telepathically tricking the famous actor Jack Vaughn to confess to the murder of Gloria Santiago's sister.

A comment made to Rictor seems to imply she no longer wishes to go by the name M. However, in a therapy session with Doc Samson, Monet stated that she hides behind the "M" persona so that others will not see how vulnerable she has become after the long time she was held captive by her brother.

[volume & issue needed] Shortly after the events of Secret Invasion, Darwin's father sells him out to a group of people called the Karma Project.

[49] Val Cooper sends Monet, Guido, and Darwin to acquire a shipment of weapons designed to take out mutants, though instead they sink it to the bottom of the ocean.

[68] After somehow getting separated from Sabretooth, M continues hunting mutants to feed off of and ends up hiding out by the Xavier Institute, now located in Central Park, New York.

All the memories of her time with the team come flooding back, which eventually breaks Emplate's hold on her, separating the two and finally curing Monet.

She's freed from Mentallo with the aid of Deathstrike and teams up with Sabretooth's Weapon X-Force to take down the cult — even going into the depths of Hell to kill Stryker for good.

[79] At a later date, The Five merged their collective power together with a Cerebro-empowered Professor X to resurrect Monet, as well as Warren, Jean, Scott, Paige, Logan, Raven, and Kurt.

The six heroes were well received by their fellow mutants back home, hailed as saviors of the highest caliber after giving their lives for preserving their newfound way of life.

[80] Claudette and Nicole St. Croix have re-appeared as members of the new mutant nation of Krakoa; they were shown at the Akademos Habitat both turned into Penance, and they were being reprehended by their sister Monet.

[volume & issue needed] Claudette along with Nicole also appeared working alongside their brother in Apocalypse's Elite Mutant Force, going by the name "The Monets".

[volume & issue needed] After returning to life, Monet renamed herself as Penance and began rallying mutants to her cause which was to seek forgiveness for their past crimes and to rebuild their world.

[volume & issue needed] Penance is immediately approached by Prophet, the leader of the human resistance who reveals that it was he that resurrected her in hope that she would aid them and that she would be more open-minded than Weapon Omega.

[volume needed] In the alternate future in the X-Men: The End series written by Chris Claremont, M is a member of the XSE and a critical part of the hastily marshalled forces attempting to defeat Mister Sinister.