The forsaken (AKA Forsaken undead) are a race of undead humans raised by the Lich King, and broke away from his grasp.
While the Lich King's grasp fell after the Third War, A large amount of undead escaped his grasp. After the grasp has fallen, these humanoids had horrible memories of torment that they had caused being mindless. The forsaken are undead humans and elves freed from the lich King, Arthas Menethil's control. They are a strong and dark force. Hailing from the Undercity, their quests were determined to end the Lich King and his Scourge. Sylvanas Windrunner is their current leader, she was a high elf ranger who lived in Quel'Thalas at the time of Arthas's invasion.
Later, after escaping the Lich King's grasp she named her "race' the Forsaken. They then joined the Horde. Ever since Putress's plague attack at the Wrathgate event, the orcs have agreed on keeping a watchful eye on these mysterious people. The forsaken never sleep, barely eat and cannot fall to an illness. Most forsaken focus on dark alchemy in a organization known as the Royal Apothecary Society, the usual people to deploy the plague. Many people wonder if the forsaken are evil, at times they can be evil, but they also try to retain their humanity when alive. Some prefer to be neutral which usually means good. Although few forsaken exist, a lot of evil ones exist as well.
Around the time of the Third War, the once beautiful and heavily populated city of Lordaeron, was invaded by Arthas's Scourge. During this specific event many citizens were killed and raised as mindless undead. The forsaken were then forced to fight anything and everything including ones they cared for. In the time, Illidan attempted to melt Northrend, the powerful magic on his Frozen Throne began to decay. This resulted in a partial amount of mindless undead to become free, many minds were almost fully restored. Ner'zhul the current Lich King at the time even lost control of Arthas. Arthas and Kel'Thuzad were later engaged into an undead civil war. Still loyal to Ner'zhul, Arthas still stayed with his master.
Illidan then attacked again and put Kel'Thuzad in charge for a short time period. With Arthas's departure from Lordaeron, three major Nathrezims, Balnazzar, Detheroc and Varimathras attempted to regain control over the walking dead. Sylvanas later defeated the three, gathred all the freed undead and named them the forsaken. Windrunner then reclaimed Lordaeron City and named it Undercity, a vast sewer system. She later made sure herself and the other damned forsaken had a home in the world. To ensure this, Sylvanas Windrunner formed an alliance with the Horde. The orcs had sympathy over this, having been controlled by demons. Among the tauren, the forsaken found a heart within Magatha Grimtotem, who gave them a cave in Thunder Bluff. They later assisted the blood elves who trust them the most.
The Darkspear jungle trolls are not very fond of them, but yet have accepted them. The Horde and the Forsaken do not really trust each other. Forsaken are cannibals. They worship the Shadow but some worship the Light, like two individuals in particular.
Second Generation Forsaken
These newly raised forsaken have glowing blue eye sockets and can spread a purple flame amongst deceased enemies. They are also more sane than the original forsaken.