Kael'thas "Kael" Sunstrider was a senior member of the Kirin Tor and the Prince of Quel'Thalas, the last of the Sunstrider dynasty. After the fall of Quel'Thalas, Kael'thas led what remained of his people in the service of the Alliance. Striving to placate his people's addiction to magic, he later covertly allied with Illidan Stormrage, the Naga and the Burning Legion. He was branded a traitor after his allegiance with the Legion was revealed. Kael'thas plotted to summon Kil'jaeden through the Sunwell, but his plans were foiled by the Shattered Sun Offensive. He was defeated by their forces in Magisters' Terrace.
Kael'thas is voiced by Quinton Flynn in World of Warcraft: The Burning Crusade and Warcraft III: The Frozen Throne.
Biography
Dalaran
Prince Kael'thas was a powerful mage and member of the Six, the shadowy high council of the Kirin Tor. Prior to the Second War, he and the other members of the high council questioned Khadgar about the orcs and the events in Karazhan that led to the death of Medivh.
During the Third War, with the Scourge invasion of Quel'Thalas, he evacuated as many survivors as he could and burned many of the enchanted forests to spite the Scourge. He assumed command over the bulk of the surviving high elves (see the fall of Quel'Thalas and Splintering) and renamed his followers blood elves in homage to their murdered brethren. He also managed to salvage the skull of his father, Anasterian, from the ruins of Quel'Thalas, as well as the broken runeblade Felo'melorn, which he later reforged.
The Hunt for Illidan
Following the destruction of Silvermoon, Kael began to notice an emptiness within himself and his brethren, an insatiable hunger and disharmony. However, there was no time to deal with that, as Kael had other duties.
Kael and his soldiers were stationed in the Silverpine Forest when a disturbance began to rile up the undead in and around Dalaran. They had begun to raid the outposts Kael had established, so he gathered up his forces to seek refuge in the relative safety on the other side of the River Arevass.
As he was loading the supply wagons, he was met by two unexpected strangers, Maiev Shadowsong and Tyrande Whisperwind. These night elves had pursued Illidan Stormrage for three days across the sea. Kael guessed that perhaps Illidan was behind the disturbances at Dalaran, and when he told them his tale, Tyrande immediately offered her assistance, thinking that he could help them track down Illidan. Maiev believed it to be a waste of time, but reluctantly agreed. With the protection of the night elves and their Mountain Giant allies, Kael quickly made his way to Pyrewood Village to retrieve his buried supply caches. As they gathered more reinforcements, Maiev asked Kael where the rest of his brethren were, and he told them of the destruction of Quel'Thalas. Tyrande empathized, but warned that vengeance and rage was not a pleasant road to walk. She also told him that one day he may lead his people to a better future.
As they arrived in Pyrewood, the undead were lying in wait and ambushed the caravan. Kael, Maiev, Tyrande and their forces battled off the first attackers, but as the second wave advanced, they realized that the caravan would never survive another assault. Maiev and Kael rushed the caravan across the bridge, while Tyrande stayed to fend off the undead alone. As she called upon the powers of Elune to protect her, the bridge fell away, and Tyrande was swept down the river. Kael wanted to pursue her, but Maiev stopped him, saying that she was a warrior and knew the risks. Maiev then demanded that Kael honour their bargain, and help her capture Illidan.
Kael and Maiev tracked Illidan to Dalaran, where Kael's scouts found him performing a strange ritual with a mysterious gem. Malfurion came and told them that Illidan's spell was using the Eye of Sargeras to break Northrend apart. Immediately, they advanced upon his location, while Kael defended their bases from the voracious undead. When Illidan's spell was interrupted, he explained that he was trying to defeat the undead, their common enemy. He had meant to destroy The Lich King at Icecrown Citadel. Malfurion refused to listen to his brother and condemned him for his part in Tyrande's death. Kael, perplexed, suggested that it was premature to assume she was dead, as she was only swept downriver, and was vehemently silenced by Maiev, who had told the Archdruid that his beloved had been "torn apart".
Malfurion, furious that he had been tricked, left Maiev entangled in vines while he and Illidan set off to save Tyrande. Maiev eventually freed herself and set off in pursuit, while Kael'thas was left in the ruins of Dalaran.
The Rise of the Blood Elves
Kael found the Grand Marshal Garithos at Dalaran, who dismissed his story of the night elves as a fanciful excuse. Garithos, Kael's commanding officer, harbored a poorly-hidden disdain for all non-human races. Garithos informed Kael that a strikeforce was encroaching on Dalaran, and that he was going to head them off at the mountains. Kael was quick to volunteer his assistance, but Garithos had other plans. He explained that a second force was believed to be approaching from the east, and that the arcane observatories needed repairs so that they could be used to spot them. Kael did as ordered, but when he came to Lordamere Lake, he found the shipyard ruined, and had no route across the water. Lady Vashj, a naga witch, soon arrived to offer her aid, citing their common ancestry. Vashj gave him boats, which Kael used to ferry his troops to the outlying observatories.
When Garithos returned from the front, he condemned Kael for consorting with the naga, despite the prince's assurances that they were not a threat to the Alliance. Garithos warned Kael that he would not tolerate treason before leaving Kael to keep things in line at Dalaran. An emissary sent by Garithos arrived the next day with further orders, reporting that the observatories had detected an undead force in the west. Kael was to defeat them, though the emissary told him that Garithos had recalled all non-elven soldiers to the front line. Kael was left with only his fellow elves to aid him, and the undead were quick to overtake the outposts across the river. Once again, Lady Vashj arrived with her naga, and though Kael was wary of accepting her offer, she insisted that without her help, he and his brethren would surely fall. Realizing that it would be impossible to survive without these reinforcements, Kael accepted. Together they defeated the undead.
After the battle, Kael told Vashj about how his people felt an emptiness ever since Quel'thalas was destroyed. Vashj explained to Kael that just like the naga, his people were addicted to magic. Without the Sunwell to give them a constant supply of magical energies, they would surely suffer a fatal withdrawal. Kael heard Garithos approaching, and bid Vashj to flee, but Garithos' men saw the naga escaping and arrested Kael and his people for treason. Garithos smugly told Kael that he now had all the proof he needed to deal with him and the other elves as he felt they deserved, and he had them all imprisoned in the Dungeons of Dalaran.
Vashj crept in through the sewers of the dungeons and freed Kael, then helped him free his brethren. Vashj promised him escape from his human oppressors through Kel'Thuzad's interdimensional portal, where her master, Illidan, was waiting on the other side. As they neared the exit, Kael met his former comrade, Jailor Kassan, who he was forced to slay in order to escape.
The group eventually left the dungeons, and Kael led his fellow elves into the portal for a mass evacuation. Garithos, intent on preventing them from escaping, sent hordes of suicide bombers to destroy the portal. Fortunately, several elf workers were discovering new towers, which Kael used to defeat the increasingly stronger mercenaries. After all the elves went through the portal, Kael and Vashj entered the portal and closed it.
Kael found himself on the barren lands of the Hellfire Peninsula, and Vashj revealed that this Outland was once the orcish homeland of Draenor. They searched for Illidan for days, until Vashj caught a familiar scent on the winds. Maiev had captured Illidan and was escorting him back to her base in a prison wagon. Kael and Vashj's forces quickly rushed into the fray and battled Maiev's army in order to retrieve the unconscious Illidan and return him to their base, where they could undo the magical lock that kept him caged.
Illidan was pleased with the tenacity of all his servants, new and old alike, and told them of the situation in Outland. To flee from his vexed master, Kil'jaeden, Illidan had fled to Outland only to find it overrun by Magtheridon and his fel orcs, reinforced by demons arriving through Ner'zhul's dimensional gates. Kael had hoped Illidan might be able to cure the blood elves of their addiction to magic, and asked if he could help them. Illidan sadly told him that there was no cure for their condition, but promised Kael that if he joined him, he would provide the blood elves with enough magical energies to keep their hunger sated forever. Upon hearing this, Kael pledged his loyalty to Illidan. The blood elf Rommath was sent to spread Illidan's message of a new homeland to Quel'Thalas.
Kael and Vashj protected Illidan as he went about closing the interdimensional gateways. Kael discovered a camp of draenei being assaulted by orcs, and lent them his aid. He was greeted by Akama, the Elder Sage, who offered his allegiance to Illidan. Finally, the time came to assault Magtheridon's Black Temple. Illidan, Kael, Vashj, and Akama all led their forces against Magtheridon's fortress, infiltrating it and finally defeating Magtheridon in his own throne room.
As Illidan stood triumphant, Kil'jaeden descended from the fiery sky and rebuked Illidan for his insolence in trying to hide. The demon gave him one last chance to save himself - destroy the Frozen Throne, or face his eternal wrath.
The attack against the Lich King
Kael and his new allies returned to Northrend, where they were immediately met by Anub'arak and his troublesome race. Though they kept them at bay, Illidan's forces slowly advanced on the Icecrown Glacier.
Arthas soon arrived with his detachment of undead. Kael, who had known the prince in the time before the war, warned him that Illidan's forces were vast, and that Arthas would never make it to Icecrown in time to save the Lich King.
When Arthas emerged from Azjol'Nerub, it was a race against time to reach the Frozen Throne before Illidan could. As Arthas and Illidan struggled to activate the obelisks surrounding the glacier, and open the gates into the Frozen Throne, Kael'thas and Lady Vashj did their best to interrupt Arthas in his struggle. Kael'thas and Arthas faced off against each other in combat several times, but Kael's forces were pushed back by the Scourge, and Arthas was able to activate all four obelisks. Arthas and Illidan met in single combat at the base of the glacier, just before the gates, now wide-open. After fierce combat, Arthas managed to get the best of Illidan, and Illidan's twitching body was tossed to the ground. Kael and Vashj were left leaderless on the snowy slopes of Icecrown as Arthas claimed his destiny. Together they took Illidan's unconscious body with them as they fled back to Outland.