Conversation so far:
What was Legion Quest?
CANNOTANSWER.
Are there any other interesting aspects about this article?
Mystique tracked down David years later to get revenge for "his" murder of Destiny.
What happened after Mystique tracked down David?
he awakened with his fractured mind healed.
David had a new goal.
What was his new goal after he awakened?
help his father realize his dream of human-mutant coexistence by killing Magneto, Xavier's greatest opponent, before he had a chance to amass power.
How was he going to kill Magneto?
He traveled twenty years into the past, when Xavier and Magneto were orderlies at the mental hospital.
Who was Magneto?
Xavier's greatest opponent.
Did he kill Magneto?
Xavier, however, leaped into the path of the psi-knife (the focused totality of Legion's psionic powers) and was killed in Magneto's place.
What was the result of his attempt to kill Magneto?
the Age of Apocalypse timeline.

Question: What happened in Age of Apocalypse?
Self-contained rewrite: What happened in Age of Apocalypse?