Find and touch the bonfires located within Blackrock Spire, Dire Maul, Scholomance, and Stratholme, then return to the Festival Flamekeeper.
We are not the only ones who celebrate this holiday, [player]. All creatures, all cultures, are touched by the flame. Even in the darkest places, the fires are being lit.
If you wish to see them for yourself, travel into the depths. Seek out the bonfires burning within Stratholme, Scholomance, among the ogres of Dire Maul, and the halls of Blackrock Spire itself; I will await your return.