Whilst the armies of the Horde and Alliance have been fighting the dangers of the Burning Legion and the Scourge a ancinet evil has been stirring beneath the depths of The Great Sea. From her undersea kingdom of Nazjatar Queen Azshara, Ruler of the serpentine race of former highborne known as the Naga, has been gathering forces to strike the surface-dwellers and retake the world that was once theirs. Striking an alliance with the crustacean Makrura the armies of the Naga enslaved the primitive Murloc race. Choosing now as their time to strike the Coalition of the Maelstrom have invaded the surface world, taking the Broken Isles and spreading further afield, to the peaceful islands of the South Seas, the shores of Kul Tiras and, if they are not soon stopped, possibly the rest of the world.
Meanwhile the Realm of Gilneas has befallen great tragedy, Worgen, attacking the isolated nation from Shadowfang Keep, have decimated the human population of Gilneas, murdering thousands of citizens and tearing down villages and towns with reckless abandon. After nearly wiping Gilneas of all human prescence some of the Worgen, possesed of unique intelligence, have decided to preserve the newly conquered lands, driving out their primitive cousins. Seeing a similar frame of mind in the Forsaken, and the use of worgen-like imagery in the Orc clans the Worgen faction have, reluctantly, joined the Horde. The new faction now have their sights set on wiping out the last few remaining Gilneans and banishing all their savage brethren to the dimension from which they originate.
On the other side of the Great Sea the World Tree Nordrassil has nearly fully healed, and the wildlife around it is gradually overcoming the legion's corruption. The Barkskin tribe of Furbolgs have grown a new home for themselves in the roots of the World Tree, raising warriors to drive back the corruption of the legion and heal the rest of Hyjal. Although much of the great mountain has recovered from the Legion's attack, a portion of the area is still under the grip of the corruption. It has become the aim of the Furbolgs to cleanse this area, defeating the Demons still remaining there and, if needs be, culling their fallen cousins. Seeking to fulfill an old debt the Chiftan of the Barkskins owed to the High Priestess of the Night Elves the Furbolgs have joined the Alliance, seeking to restore the world to the beauty it possesed befor the Third War.