Originally Posted by
Fleugen
We don't stop the Legion. We already know how the final raid ends, and whether you've read it or not, we know that Illidan sacrifices himself in some way to trap Sargeras, along with what remains of the souls of the Titans, to seal him away. Presumably forever, but given that yet another prophecy is Anduin leading the Army of Light, we know the Army of Light isn't done yet.
Were it not for Illidan, the Legion would still exist after Legion. We don't stop them - HE does.
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We already know what happens to Illidan. Datamining is a powerful tool. I recommend looking it up, unless you're trying to avoid spoilers.
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Do we know this? As far as I'm aware, X'era hasn't been leading the Army of Light against the Void Lords, so why would she be taking away the most powerful weapon against the Legion for a fight she hasn't been leading, BEFORE the fight against the Legion is even over?
Additionally, why would Turalyon be ok with Alleria delving into the Void for power, knowing full well his war is against the Void? I don't think X'era has even begun a war against the Void, or Turalyon would be spearheading the assault against it.
That said, I could be wrong. I didn't pay much attention to the Light's Heart quests.