Astonishing X-Men #5 (2004)

The X-Men track the killer to a semi-functional spaceship at Chapanga Beach. They find the man working on something he calls a Ghost Box. After a difficult fight Cyclops orders the team out of the ship and has Storm shoot it down with lightning. Storm is distressed that Cyclops's orders might have resulted in her killing the man, but Cyclops is unapologetic. The man is still alive, but chooses death rather than revealing more about his purposes beyond referring to "the Annex".

Puzzled by the box they retrieved at Chapanga Beach, the X-Men call in Agent Brand. She tells them it's a Ghost Box, and that it's used for travel between parallel worlds. The team also finds out that the coordinates for "Tian" from the notebook they found match a spot in China known as the Dead Five Miles, in which nothing may be detected. They go there, and discover the floating retreat of a group of mutants who apparently died on M-Day.

The X-Men explore Tian and find a few remaining residents with surprising information.

The X-Men interrogate the mutants who attacked them at Tian and decide to pay Forge a visit.

Forge reveals his plan for dealing with the alternate dimensions of the Ghost Boxes to the X-Men.

This appears to be an account of how Agent X-13's mission on Earth-616 would have gone had he targeted and killed Cyclops first instead of targeting Wolverine. The X-Men rapidly fall apart, and Agent X-13's homeworld sends in "Deathlok-class Security units", which look like Sentinels. One of them had what appeared to be Magneto wired into its chest. They quickly subdued the entire world amidst a staggering loss of life, including the use of nuclear weapons. But Agent X-13 considers none of that to be his problem because he's just a field agent.

This story follows what would have happened if Agent X-13's request to target Earth-889 had been granted. Earth 889 is a Steampunk reality, in which Miss Emma Frost leads the X Society from her mansion in New Portsmouth. Using their superior aircraft, they catch up with Agent X-13, but a mishap involving his fireballs and Logan's claws cause a fatal dirigible explosion and crash. As a result, the X Society becomes exiled overnight, with "sentinels" posted outside the mansion. Miss Frost speculates that she may decamp to Europe and possibly even allow Scott to marry her as he has long desired.

In a world where Cyclops decided to approach Subject X cautiously instead of letting Wolverine take him out quickly, a suicidal Scott Summers is the only X-Man surviving in a ruined mansion filled with ghosts.

In a world where the annexation took several years, Hisako journeys to a supposed evacuation point with a deranged Hank McCoy and a Logan who is confined to a wheelchair due to the adamantium on his legs being warped early in the fighting.