Many months have passed since Archimonde and the Burning Legion were defeated at the Battle of Mount Hyjal...

The stalwart night elves, led by the Arch Druid, Furion Stormrage and the Priestess Tyrande Whisperwind, have vanished back into the shadows of Ashenvale Forest - intent to heal the ancient lands that were scarred by the Legion's vile corruption.

The battle-weary orcish Horde, led by the idealistic Warchief, Thrall, has settled in the harsh, eastern hills of the Kalimdor Barrens. Finally able to claim a homeland of their own, the orcs work tirelessly to found and protect their new nation of Durotar.

The human survivors of Lordaeron, under the command of the Sorceress, Jaina Proudmoore, have also settled along the eastern coast of the Barrens. The island citadel of Theramore was erected to safeguard the last, rag-tag remnants of the failing human Alliance.

...And Arthas, the newly crowned King of Lordaeron, has driven the undead Scourge to eradicate the last vestiges of resistance to his iron rule. His kingdom - the once proud bastion of human might and nobility - has become a plagued realm of death and sorrow. Now, driven by haunting visions of the Frozen Throne of Icecrown, Arthas plans to tighten his grip over the rest of the world.

...Still, one dark soul still remains at large...

For in some shadowed corner of the world, the wayward creature known as Illidan Stormrage plots... and awaits...

*from the official Blizzard Warcraft III site