That's Not Canon!

That's Not Canon! is a dungeon & raids achievement earned for defeating Mannoroth in Well of Eternity on Heroic difficulty after dealing enough damage to Mannoroth while Varo'then is still alive to cause him to sacrifice Varo'then to heal himself.

Trivia

 * The name is a reference to many players getting mad about retcons throughout Blizzard's games, and that in World of Warcraft, they actually create a retcon of Varo'then's death as he is not killed by Malfurion, but rather by Mannoroth.