The first of many AvX stories started with Professor X on a solo mission to the center of the Earth to hunt down Lucifer, equipped only with a special wheelchair with tank treads…
…and quickly escalated to the X-Men fighting The Avengers because the Avengers wanted to help out.
But before the battle, The Avengers clear the area.
We don’t know this yet, but Lucifer is actually an alien who caused Professor X to lose the ability to walk.
X beats Lucifer in the end, of course. And it took him 10 years to hatch this plan.
Ten years. And in all, it wasn’t that hard to beat him.
Creators: Lee, Kirby