Hollow (formerly called Penance) is an apparently mindless body which had three members of the St Croix family, all members of the Marvel Comics superhero team Generation X, had been trapped in at some time. The body possesses red diamond-like skin and rarely speaks.
Penance was created by Emplate as a prison for his sister Monet. Emplate is imprisoned by Claudette and Nicole before being trapped Monet grabbed Penance trapping her with him.
Later Penance appeared on the Massachusetts Academy lawn and joined Generation X. When the team finds out that M is trapped in Penance her twin sisters free her and take Monet's place.
The twins were eventually freed and Penance had no more people in side her she became a living hollow diamond shell.
After leaving Generation X Hollow joined a new team the Loners.