And how exactly does Prisoner M-13 constitute a "dangerous individual"? Granted, he's the world's foremost authority on genetic mutation -- but that doesn't make him a mutant. He's confined to a wheelchair, for God's sake! 
Appearing in "Prisoner M-13"
Featured Characters:
Supporting Characters:
- Nina (First appearance)
- Renee Majcomb
- Henry Peter Gyrich
- Dr. Ingrid Thysson
- Daryll Smith
Antagonists:
Other Characters:
- Avengers (Mentioned)
- Fantastic Four (Mentioned)
- Hulk (Bruce Banner) (Mentioned)
- X-Men (Mentioned)
- Onslaught (Mentioned)
- Adolf Hitler (Mentioned)
- Committee on Mutant Affairs (Mentioned)
- Val Cooper (Mentioned)
Races and Species:
Locations:
Synopsis for "Prisoner M-13"
In the aftermath of the Onslaught event, a de-powered Charles Xavier is incarcerated as prisoner M-13 in an abandoned Hulkbuster Base. Dealing with his guilt, and worried what Bastion plans for the future of mutantkind, he soon finds an ally in the curious creature M-9 (Nina) - a little girl with tremendous mutant powers. She informs Charles that his powers are not gone, and she can help him turn them on again - he is happy, but refuses, wishing to first deal with the darkness inside him. Events move to terminate Nina before she becomes too dangerous for Bastion's staff to handle, but Xavier and Ingrid Thysson cause a distraction, allowing the undercover mutant Daryll Smith to fake Nina's death and let her escape. As Valerie Cooper drives her to safety, she uses her powers to create a teddybear phone in Xavier's cell to call him and say she is safe, and thrilled to finally see the surface.