The War of the Ancients and the Sundering

The night elves rose beside the Well of Eternity, a lake of raw arcane power at the heart of the single super-continent of Kalimdor. Their queen, Azshara, grew so drunk on that power that when Sargeras whispered to her, she agreed to tear open a portal and let the Burning Legion in.

The first great invasion nearly ended the world. A desperate alliance of night elves, dragons, and demigods fought the Legion's commanders Archimonde and Mannoroth to a standstill. When the Well was destroyed to sever the Legion's anchor, the backlash shattered Kalimdor - the Sundering - drowning most of it and leaving the continents and the churning Maelstrom in its place.

Azshara and her court were dragged beneath the sea and twisted into the serpentine naga. Illidan Stormrage secretly hoarded a vial of the Well's water and created a second one, an act that saw him imprisoned for ten thousand years - and set up his role in wars still to come.