The Mutant X-verse; when Havok swapped psyches with an alternate Earth version of himself, this is the reality to which he traveled to.
Havok when "killed", passed through a dimensional rift and ended up in another reality where he possessed his counterpart's body (who had just died). In this reality he was the only Summers on Earth, his family having died when the plane exploded. After which he ended up in an orphanage and then under Xavier's foster care. He became Havok, one of the founders of the X-Men and would fall in love with Madelyne Pryor who he would later marry and have a child with named Scott.
Xavier would end up absorbing the Shadow King's essence, after which Magneto a co-founder of the X-Men, would lead the team through various trials of fire. Angel would become the Fallen, Storm would become the vampiric Bloodstorm, and the Beast became Brute. To improve human-mutant relations, Havok formed X-Factor which would eventually break ties with the government, becoming the Six.
As Havok was getting used to the new reality, the Six were called by the government to stop the release of the Legacy Virus by the terrorist organization S.H.I.E.L.D. During the fighting, the cosmic Goblin Force brought Madelyne under its thrall. Madelyne would become the Goblin Queen, seeking to conquer the world. Only to be stopped by her child Scott who used his growing powers to force the Goblin Queen out of her. Which ended up in the Earth's core, merging with Beyonder's corpse.
Due to the Goblin Queen's actions, anti-mutant sentiments grew. The Six recruited two new mutant members, Gambit and Captain America. They rescued mutants and fought against S.H.I.E.L.D. oppression. When the Six attempted to enter Canada, they were forced to battle the Avengers. During the battle, Havok was forced to fight an out of control Captain America. The Moon was shattered by the energy released. Which revived the Goblin Force deep in the center of the Earth.
Many heroes were killed by the Goblin Queen in her search of the Nexus of Realities which had been unwittingly absorbed by Havok. The remaining surviving heroes were assembled at Magneto's citadel in Antarctica by Doctor Strange. A device to unite their power with that of Havok was designed by Reed Richards. Havok confronted the Goblin Queen, drew it into the Nexus, restored Madelyne to life and sent himself through another dimensional rift, eventually ending up back home at Earth-616. 
Cast of Characters:
- Apocalypse (En Sabah Nur)
- Ariel (Jean Grey)
- Black Widow (Natalia Romanova)
- Bloodstorm (Ororo Munroe)
- Brute (Hank McCoy)
- Captain America (Steve Rogers)
- Deathlok (Luther Manning)
- Fallen (Warren Worthington III)
- Famine (Autumn Rolfson)
- Hawkeye (Clinton Barton)
- Ice-Man (Bob Drake)
- Magneto (Erik Lehnsherr)
- Marvel Woman (Madelyne Pryor)
- Polaris (Lorna Dane)
- Rogue (Anna Marie)
- Typhoid Mary (Mary Walker)
- War (Abraham Kieros)
- Alpha Flight
- Fantastic Four
- Lethal Legion
- 171 characters that originate from Earth-1298
- 15 teams that originate from Earth-1298
- 5 organizations that originate from Earth-1298
- 1 locations that originate from Earth-1298
- 43 appearance(s) of Earth-1298
- 464 image(s) of Earth-1298