I was king of this empire once, long ago. In life I stood as champion. In death I returned as conqueror. Now I protect the kingdom once more. Ironic, yes? -Anub'arak
Anub'arak is the king of the merciless Nerubians, and a high-ranking member of the Undead Scourge.
The Spider Wars
Anub'arak was once king of the mighty Nerubians, a race of spider-like alchemists and scientists. When the evil Lich King took up residence in Anub'arak's homeland of Northrend, Anub'arak's people caught the Lich King's eyes. The Lich King sought to slaughter the Nerubians by spreading a deadly disease throughout the Nerubian empire. Anub'arak and the Nerubians were immune to the disease however, so the Lich King began a full-scale invasion on Azjol-Nerub. The Nerubians were no match for the Lich King's undead hordes, and they were forced to flee below Northrend. While digging, the Nerubians re-awoke the evil Faceless Ones, minions of the mysterious Old Gods. The Nerubians were unable to dig any further, and they were murdered by the undead. Although the Nerubians were immune to the plague, they were not immune to resurrection, and were raised into undeath as unwillingly serve the Lich King. Anub'arak was among the majority of Nerubians who were killed and resurrected.
Meeting With The Archmage
After his resurrection, Anub'arak meet with the exiled wizard, Kel'Thuzad, who wanted to wield great power. Anub'arak spoke with Kel'Thuzad about the Scourge and its evil master while they walked through the fallen Nerubian capital, Azjol-Nerub. Anub'arak later took Kel'thuzad to the necropolis, Naxxramas. There, Kel'Thuzad witnessed horrific acts, including the murder of a sickly woman. Kel'Thuzad fled Naxxramas, only to join the Scourge later.
The Race To Icecrown
When the Lich King called for his new Death Knight, Arthas Menethil, to protect him from the demon / elf hybrid, Illidan Stormrage, Anub'arak was ordered to assist Arthas in his journey through Northrend. When the two found out that Illidan and his lackeys, Kael'Thas Sunstrider and Lady Vashj, were already ahead of them, Anub'arak lead Arthas and an army of Scourge through the hidden tunnels of Azjol-Nerub. This was no simple task, however, when the Facecless Ones, living Nerubians, and a team of Dwarf explorers attempted to stop the undead. Anub'arak and Arthas slew most of the Dwarves and living Nerubians, and in time defeated the leader of the Faceless Ones in Azjol-Nerub. Near the end of their adventure, Arthas and Anub'arak came across a Forgotten One, an ancient and mysterious creature that possessed great power in the service of the Old God, Yogg-Saron. Anub'arak and Arthas made it to Icecrown, capital of the Scourge, to end the threat from Illidan. While Arthas battled Illidan, Anub'arak slaughtered Kael'Thas' Blood Elf forces. When Illidan was defeated, the remains of his armies fled and Anub'arak returned to Azjol-Nerub to rule the undead Nerubians, or Crypt Fiends as they were then called.
War In The Frozen Wastes
When the forces of the Alliance and Horde assaulted Northrend in an attempt to end Arthas' reign of terror, Anub'arak remained in Azjol-Nerub to command the Crypt Fiends. After the Scourge's defeat in the Borean Tundra at the death of Prince Valanar, the heroes of Azeroth moved on to the dragon holy ground of Dragonblight. There, the heroes stormed Azjol-Nerub to kill Anub'arak. The heroes reached Anub'Arak's throne and fought bravely, killing the Crypt Lord in his own home.
The Argent Tournament
At the Argent Tournament, the heroes jousted and battled each other to determine who was powerful and worthy enough of taking part in the assault on the Lich King's citadel. When a group of adventurers took the Trial of the Crusader, they were challenged with bloodthirsty beasts, demons, and enslaved Scourge. They defeated everything that was thrown at them, but as they finished the trial, the Lich King himself arrived. He shoved his legendary runeblade, Frostmourne, into the arena floor. The floor cracked and fell into a pit, taking the heroes with them. What they saw was not what they expected. An old enemy thought dead - Anub'arak, revived. Anub'Arak was resurrected by the Lich King soon after his defeat at Azjol-Nerub to terrorize the Tournament. The heroes battled the ancient spider king and his minions. In the end, Anub'arak was slain once and for all, allowing him to finally rest in peace.