Balnazzar

Balnazzar (formerly under the guise of Saidan Dathrohan, Grand Crusader of the Scarlet Crusade) was one of the three nathrezim siblings left behind in Lordaeron to oversee the demonic conquest of that land. The return of Prince Arthas, following the defeat of Archimonde, sent the three brothers packing, but they quickly regrouped and concocted a new plan to destroy Arthas once and for all. Though they (and Sylvanas Windrunner, who attacked Arthas on her own terms) didn't destroy Arthas, the undead prince left Lordaeron, leaving Balnazzar to rule the Plaguelands. Soon after, Sylvanas (who forcibly made Varimathras join her) laid siege to Balnazzar's forces and ultimately forced Varimathras to execute Balnazzar. However the execution was faked and Balnazzar later came to possess the body of Saidan Dathrohan, a founder of the Scarlet Crusade.

Following the war against the Lich King, Balnazzar and his undead Risen were killed by adventurers. Forced back to the Twisting Nether, he returned years later during third invasion of the Burning Legion. Deciding to dismantle the newly reformed Knights of the Silver Hand, he serves as the main antagonist of the paladin class order campaign. Balnazzar was finally killed in the Netherlight Temple located in the Twisting Nether, ending the dreadlord permanently.

The breaking of Ner'zhul
At Kil'jaeden's command a group of dreadlords consisting of Balnazzar, Tichondrius, Detheroc, Mal'Ganis, and Varimathras tortured the orc shaman Ner'zhul after he had escaped from Draenor to the Twisting Nether. Eventually, Ner'zhul, his sanity cracking, would agree to serve Kil'jaeden. Kil'jaeden passed the orc's spirit through death and revived as a spectral entity. The dreadlords bound his disembodied spirit to a specifically crafted set of armor and a mighty runeblade called Frostmourne. These items were locked in a diamond-hard block of ice to imprison Ner'zhul. The Lich King and the dreadlords who had tortured him were then sent to Azeroth in order to weaken any resistance that the Burning Legion would face in during the Third War. While the Lich King gathered his strength, Balnazzar and his fellow dreadlords would serve as jailors and executors meant to hasten the Lich King's task by any means necessary. To this end, they would construct the Icecrown Citadel within Northrend. Though seemingly broken by the dreadlords, Ner'zhul sought vengeance and was able to play on the dreadlord's fears of Kil'jaeden in order trick them into allowing him to hurl Frostmourne out of the Frozen Throne.

The Third War
Balnazzar and his brothers, Varimathras and Detheroc, were not aware that the Burning Legion had been defeated at Mount Hyjal until months after the fact. It was only when Arthas returned from his sabbatical to Kalimdor that he announced Archimonde's destruction. Arthas stated that their deaths would complete their folly. Balnazzar and his brothers quickly teleported away before Arthas could strike.

The dreadlords plotted in the safety of the Tirisfal Glades, and began to form a plan to ruin the undead king. Knowing that Ner'zhul, and Arthas, were losing their powers, they called to Sylvanas, who was no longer locked in loyalty to the Lich King, and asked for her assistance in the coup that was sure to entail. Sylvanas, hungry for vengeance for her current form and the slaughter of her people, agreed. Balnazzar and his brothers staged an ambush for Arthas within the Capital City ruins, separating Kel'Thuzad from him and attacking him with their minions. Balnazzar even loosed other dreadlords on him, but Arthas, rounding up the forces he could find still loyal to him, escaped, or so he thought.

Escorted by a cadre of banshees, Arthas was attacked by Sylvanas, who had prepared a long, grisly death for her murderer, and was about to begin her work when Kel'Thuzad interrupted and chased her off. Though he still lived, Arthas was gone from Lordaeron, or the Plaguelands as they were now called, and Balnazzar was free to reign over it as he liked. He sent Varimathras to bring Sylvanas to join their new order, but things went horribly awry.

Unfortunately for Balnazzar, Sylvanas had plans of her own and laid siege to Lordaeron. She had defeated Balnazzar's brother Varimathras, who offered to serve her in exchange for his life. Sylvanas accepted and the dreadlord fought at her side in the attack on Lordaeron. Balnazzar received word from his scouts that Sylvanas had coerced Varimathras to her side, killed Detheroc, and allied with his human minion, Garithos. The banshee and her forces laid siege to Balnazzar's base, which he had fortified within the city ruins. Even armed with demons as his minions, Balnazzar found himself attacked from both ends by Sylvanas and Garithos, and despite his many threats, Balnazzar's forces were defeated.

Following their victory Sylvanas, Varimathras, and Garithos approached Balnazzar. Sylvanas ordered Varimathras to kill his brother as a testament to his loyalty to her. Varimathras was reluctant as killing another nathrezim was forbidden, but Sylvanas was adamant. Balnazzar was sure that Varimathras would never take that final step and was apparently destroyed.

The Ashbringer
Unknown to Sylvanas, Balnazzar lived, having staged his death with his brother, and went underground within the Plaguelands. Not content to simply sit by while the undead legions overran Azeroth, he formed a new plan to oppose them. He also sought to establish a means to protect himself by creating a new army. While he was stuck between worlds of the living and dead, he killed the paladin Saidan Dathrohan and possessed his body. He then helped found the Scarlet Crusade, an order of knights focused on the singular goal of defeating the Scourge in all its forms. Recognizing that he wouldn't be able to twist Alexandros Mograine into his service, Balnazzar manipulated Alexandros's son Renault Mograine into killing his father with the Ashbringer. While Alexandros would be raised by Kel'Thuzad into service of the Scourge, a schism would cause a group of paladins to form a new order known as the Argent Dawn. Left unopposed, Balnazzar established control over the Scarlet Crusade, which soon became synonymous with corruption and extremism.

Legends: A Cleansing Fire
When fanatic members of the Scarlet Crusade raided a village, the raid leader Sir Thomas mistakenly killed his own family. Becoming mad upon this revelation he attacked his fellow crusaders and was ultimately slain, after which he became completely mad. Soon after his death, Balnazzar transformed Sir Thomas into the Headless Horseman.

World of Warcraft
Balnazzar was the final boss of the live side of Stratholme. He used to begin the fight as Grand Crusader Dathrohan, but eventually shed his human disguise for his true form. Once slain, his head was delivered to Duke Nicholas Zverenhoff.

Cataclysm
After the Cataclysm rocked the world, Balnazzar slaughtered the Scarlet Crusaders in Stratholme and transformed them into the undead creatures they once hated, using his necromantic powers to resurrect them as the Risen. He also taught the Risen Hammersmith to make demonic weapons. Eligor Dawnbringer tasked adventurers to slay him. His weapons and armor - Demonshear, the Hammer of the Grand Crusader, the Crown of Tyranny, the Shroud of the Nathrezim, and the Book of the Dead - were recovered from his body and stored in the Sanctum of Light.

Legion
Balnazzar is one of the many demons that crossed the portal inside the Tomb of Sargeras to attack the forces of Azeroth in the climactic, disastrous battle at the Broken Shore.

When Tirion was captured, Balnazzar guarded the Ashbringer in order to ambush and take the body of the one who claimed it. Though he failed, he swore to return in time, saying to the new wielder of the Ashbringer that their "journey together has only just begun."

Balnazzar later led an attack against the Conclave priests of Netherlight Temple, and the Knights of the Silver Hand arrived to aid the priests in its defense. As Balnazzar began to summon in more demons, a dreadlord infused with the Light named Lothraxion, High Commander of the Grand Army of the Light, arrived, sent by High Exarch Turalyon. Lothraxion assisted the Highlord of the Silver Hand and the High Priest of Netherlight Temple in defeating Balnazzar.

As Netherlight Temple is located deep in the Twisting Nether, and demons can truly be killed only in the Nether, Balnazzar (along with the reinforcements he summoned during the fight) is dead for good.

In the RPG
Brann Bronzebeard misspelled his name as Balzannar.

Balnazzar also uses agents to do his jobs. One day a mysterious prophet emerged from caverns underneath the Stonetalon Mountains. The prophet warned that the Burning Legion was coming soon and would be ushered in by the Forsaken and sent adventurers on anti-Forsaken missions. Upon further investigation, it was found that the "prophet" was really an agent of Balnazzar, who had survived his "death". Balnazzar had plotted his revenge against Sylvanas ever since that day — and the prophet was apparently just one small part of his plan.

Possessed soul
No one in the Crusade is aware that Dathrohan is a demon — they simply believe him to be a holy knight obsessed with the destruction of the undead. Balnazzar uses this fact to his advantage as much as possible, intending not only to defeat the undead but one day secure his hold on Lordaeron once again. To maintain his charade, Balnazzar kept (and still keeps) a low profile, letting others run the Scarlet Crusade. At present, Balnazzar dwells within the Scarlet Crusade stronghold in the besieged ruins of Stratholme, in the deepest reaches of the Eastern Plaguelands. The Scourge and the Crusade remain locked in battle, at a stalemate primarily because Balnazzar depends upon his masquerade for his long-term plans. His agents actively recruit new members for the crusade, and his ranks grow steadily. Should anyone find out his true nature, however, the Scarlet Crusade could potentially fall apart overnight, and the undead would become the only power in the Plaguelands.

Balnazzar attempts to remain in his possessed form as long as possible, not revealing his true nature until absolutely forced to do so. He avoids using spells or spell-like abilities unless they could be paladin spells or he can do so in a way that makes them look like they came from a magic item. He avoids direct combat, preferring to let his minions do the fighting for him. If cornered and sorely pressed, he reveals his true nature, abandoning his possessed body and emerging in all his glory. The hulking demon's skin is a waxy purple, save the black bat-like wings. Its eyes glow crimson as it raises its massive greatsword. At this point, he lets loose with all the firepower at his command, subduing and then destroying his enemies with demonic fury. Any allies who remain by his side are then slain in turn, so that he may preserve his secret, and he returns to his former body to maintain the masquerade. If his secret is openly revealed, he retreats, seeking vengeance on those responsible at some future time. Balnazzar can possess the body of a creature he has slain through the use of his energy drain ability. In doing so, his form turns to a misty cloud that invades and takes over the corpse, while the soul of the slain creature moves on to its final reward (or punishment). The slain creature cannot be raised from the dead through any means other than a true resurrection for as long as Balnazzar possesses it (True resurrection ejects him from the body at once). His power sustains the body so it does not decompose; in fact, it appears in all respects as if alive. Balnazzar wears paladin gear (Scarlet Crusade armor and the like) in Saidan Dathrohan's guise. Otherwise, he carries a greatsword of wounding; this sword is tied to Balnazzar's life force, and anyone else touching it or trying to wield it is corrupted as long as he contacts the weapon. If Balnazzar possesses a creature, the sword vanishes with him, returning to his side when he emerges. Balnazzar also has a ring of protection and wears bracers of armor.

Ashbringer

 * My kind are called Nathrezim. Dreadlords, in your tongue. Perhaps Thal'kituun would be more fitting. It means unseeing guest in your language. Fitting because I have existed here, between the world of the living and the dead, awaiting a moment such as this, under the very noses of the scourge—without their slightest suspicion.
 * Know that I am Balnazzar. Know, as I drink your life, that I will take up residence in this weak shell your soul once called home. Know that I will corrupt and destroy everything and everyone you have ever loved. (killing and possessing Saidan Dathrohan)
 * Fleeting are the moments, these days, in which I may truly be myself... That I may rend flesh, shed blood, and shiver bone. Not as the mortal Dathrohan...But as the undaunted and redoubtable nathrezim Balnazzar. Cheater of Death, Master of Mortal Pawns... And Bane of You Rotting Dead! (Said while killing an abomination, when defending Hearthglen)

Notes and trivia

 * When he was under the guise of Saidan Dathrohan, Balnazzar was seen using the sword Demonshear.
 * Two realms in World of Warcraft are named after Balnazzar: Balnazzar Europe and Balnazzar US.
 * Balnazzar is voiced by Marc Graue.
 * In the Warcraft III campaigns, dreadlord characters were given different colors out of concern that players wouldn't be able to tell them apart.