Scarlet Witch A Moment in Marvel History.

This is from the House of M story Arc.

After the Scarlet Witch's reality warp, the mutant population was severely reduced, with only an estimated 198 left with their powers. Among those depowered were the X-Men's founder Professor X and his nemesis Magneto. Because of this event, mutants are no longer the primary line of evolution, and because of their dwindled genepool, may be considered an endangered species, on the brink of extinction. Whether this latest development will stand the test of time, or if it will eventually be negated, remains to be seen.

Many of the mutants that retained their abilities were relocated to a tent city on the grounds of the Xavier Institute, "protected" by Sentinel Squad O*N*E. Since this group includes many former X-Men villains, the arrangement was strained at best. After learning that early U.S. government estimates cited only 198 mutants remaining, those mutants living on the Xavier Institute grounds sought a symbol to rally around and adopted the name "198" for themselves.

Recently, X-Force organized an assault in the X-Mansion to free the 198 from the grounds, leading them to an abandoned military base. However, they were founded by some of the X-Men, and also by Bishop and his squad, which was attacked by Cyclops (Johnny Dee manipulated Cyclops). The confrontation began, and they knew that the military base would be destroyed, with 198 inside.Val Cooper discovered the manipulation of Johnny Dee and warned Bishop, who asked for the confrontation stop. Iron Man and Ms. Marvel arrive to help, and with effort, they save the 198, which once received the freedom to leave the X-Mansion.

* Note: The number 198 is an early U.S. government estimate of the total number of mutants remaining on Earth, not a definitive census. The 198 have therefore chosen that number as a symbolic value, not as a count of their members.