Scourge

First introduced in Warcraft III, the Scourge is an army of Undead created by the Lich King to destroy all life on Azeroth. It includes undead humans, elves, Nerubians and several other assorted races. The Scourge was created by the Burning Legion as a means of weakening the races of Azeroth, primarily the Human Alliance, to prepare for the invasion of the Legion itself. The Legion captured the spirit of the former Orc Shaman Ner'zhul and forced him to become the Lich King, the power and mind behind the Scourge. As Ner'zhul's power grew, he began to become powerful enough to corrupt paladins to join the Scourge as Death Knights, one of these being Arthas Menethil, heir to the human kingdom of Lordaeron. Ner'zhul began crafting a plan to break out of his imprisonment, and to break away from the Burning Legion. When Kil'Jaeden realized what he was up to, he sent Illidan to destroy the Frozen Throne and Ner'zhul to end his treacherous endeavour. However, Ner'zhul commanded Arthas, his new champion, to come to his aid. Arthas fought Illidan and defeated him, then went to Icecrown and shattered the Frozen Throne, putting on Ner'zhul's helm. Ner'zhul's soul merged with Arthas' mind and body, and they became one of the most powerful beings on Azeroth.

Now, Arthas seeks to rebuild the Scourge, and he prepares to invade Azeroth once more.

Introduced in Warcraft II: Tides of Darkness, goblins are diminutive, green-skinned humanoids. The goblins as a whole have always been neutral, however a number of goblins joined the Horde during the timeframe of Warcraft II. Goblin mercenaries are recruitable in Warcraft III.