 The Grey Havens , an Elven port on the western shores , is attacked by the Corsairs of <unk> , allies of Sauron . The Dwarves , who have been reluctant to ally with the Elves , eventually decide to come to the aid of the Grey Havens . With the Goblins defeated and all of Eriador pacified , the Dwarven @-@ Elven alliance is tested by Sauron 's forces . Mordor 's overwhelming forces besiege the Lake Town of <unk> and the Dwarven city of Erebor . The Dwarven king Dáin leads a small group of Dwarves and men of Dale to defend their homeland and manage to eliminate the Mordor presence in <unk> but are forced to retreat back to Erebor to defend themselves against an overwhelming army led by the Mouth of Sauron . After a long battle against the Mouth of Sauron 's army , Elven reinforcements from Mirkwood led by the Elven king Thranduil arrive and save the Dwarves , defeating the Mouth of Sauron and his army . Elrond leads the first attack , but later , Thranduil , Glorfindel , Glóin , Arwen , and King Dáin all unite under the Dwarven @-@ Elven alliance for a final battle in Dol Guldur , the stronghold of Sauron in Mirkwood , aided by the Ents and Eagles . The Good forces and its three combined armies overcome the defenses and destroy the fortress , eliminating the last threat in the North . 
