Kael'Thas Sunstrider is among the most well-known villains in all of World of Warcraft, although he certainly didn't start out that way. As many villains often do, Kael'Thas had good intentions but turned to evil to accomplish them. For Kael'Thas, his pride and his addiction to Fel magic quickly turned him from the revered last member of the Sunstrider lineage to a hated traitor to the Blood Elf people.
In World of Warcraft: The Burning Crusade Classic Kael'Thas is a boss within both Tempest Keep and Magister's Terrace. He also appears as a friendly NPC in Silvermoon City, standing by his advisors in the Sunspire. Kael is always accompanied by his three iconic Verdant Spheres and is a much more difficult boss in Classic than he is in timewalking dungeons.
10 Prince Kael'Thas Led The Blood Elves to Outland
Kael'Thas Sunstrider was the only son of King Anasterian Sunstrider and the last of the Sunstrider name. He was the de-facto leader of the Blood Elves, but not its king, as he did not feel fit to wear the crown upon his father's passing. Instead, he ruled as Quel'Thalas' royal prince.
When the Blood Elves were nearly wiped out after an attack by the Scourge, and their sacred Sunwell tainted, Kael'Thas led the Blood Elves to Outland in pursuit of a new source of everlasting magic.
9 He Was Once A Senior Member of the Kirin Tor
Kael'Thas was once a member of the Council of Six, the High Council of the Kirin Tor in Dalaran. The Council of Six was made up of the most senior members of the Kirin Tor, who oversaw the activities of the legendary magical city both internally and externally.
This is a big deal and signifies Kael'Thas' institutionally recognized magical ability – especially when other former members include the human Kel'Thuzad, Medivh's Apprentice Khadgar, and Lady Jaina Proudmoore.
8 His Three Verdant Spheres Originate From The Sunwell
Kael'Thas is an iconic character in World of Warcraft, but perhaps he would not be so iconic if not for the three floating spheres that surround him at all times. Kael'Thas did not always have these spheres: in fact, he only received them just years before the events of The Burning Crusade played out.
When Arthas and his death knights attacked Quel'Thalas, they not only killed King Anasterian Sunstrider, they also tainted the Sunwell. Kael'Thas and several other powerful mages decided to destroy the source of the blood elves' magical affinity with the help of three mooncrystals, all of which survived the Sunwell's destruction.
7 Kael'Thas Has A Thing For Jaina Proudmoore
Despite being the de facto ruler of the Blood Elves and a member of the most prestigious magical council on all of Azeroth, Kael'Thas was a pretty suave guy. While in Dalaran, Kael'Thas thought fondly of the young Lady Jaina Proudmoore. While she took a liking to him too, she also had feelings for the Prince of Lordaeron, Arthas Menethil.
When Arthas wiped out 90% of the blood elves and all but destroyed Quel'Thalas, Kael'Thas told Jaina that she had chosen a murderer instead of him. He left all thought of being with her behind in Dalaran as he swiftly traveled to his homeland to fix what could be recovered.
6 Kael'Thas Fought Arthas Directly Alongside Illidan
Kael'Thas and Illidan worked together before, during the siege of The Frozen Throne. Illidan's plan was to use the Eye of Sargeras to utterly destroy the Frozen Throne, and take with it the Lich King, the Scourge, and some portion of the Burning Legion's power over Azeroth.
Kael'Thas led a large-scale dragonhawk ambush, only to be thwarted by the Arthas' new Nerubian allies. Kael'Thas fought Arthas directly, evenly matched for some time, before teleporting away.
5 To Satisfy Mana Addiction, He Turned To Fel Magic
In Outland, Kael'Thas hoped to find a new magic source to satisfy his people's mana addiction after the destruction of the Sunwell. He discovered the ability to drain magical power from other living beings from Illidan, and taught his people back in Quel'Thalas that it could quell the cravings for a short time.
Some of his followers became devout followers of Illidan, though, and Kael'Thas felt excluded. He turned to Fel magic too, finding it to be an abundant source to satisfy his addiction. In the end, though fel magic corrupted his mind completely.
4 Kael'Thas Became An Agent of the Burning Legion
Kael'Thas once fought against the Burning Legion and its influence throughout Azeroth and Outland. Kael'Thas became unstable under the influence of Fel magic, unable to truly harness its powers in a way that wouldn't gnaw at his thoughts.
Kil'Jaeden approached the turbulent prince with a proposal: leave Illidan, and he would learn how to harness the secrets of the Fel. The prince initially refused, but after paranoia led him to believe he had failed his people and to believe Illidan was his enemy, he returned to Kil'Jaeden.
3 His Pride Was His End
Kael'Thas did not want to return to Quel'Thalas without a replacement for the Sunwell, nor did he want to return as an insane Fel-addled prince; he had previously made fun of orcs for their reliance on the Fel, after all.
After his defeat in Tempest Keep, he retreated to the Magister's Terrace, still unable to comprehend that he had been bested and that his selfish schemes were over. His famous line, "Tempest Keep was merely a setback!" has become one of the most quoted lines in all of World of Warcraft.
2 Blood Elves Consider Kael'Thas A Traitor
While Kael'Thas was the last of the Sunstrider lineage and did much to try to improve the lives of the remaining Blood Elves after their near-annihilation, his decisions led to his becoming an outcast. With time, the Blood Elves learned of his treachery with the Burning Legion and turned against him entirely.
Kael'Thas' very name is something of a four-letter-word in Silvermoon City. When one allies with the forces responsible for the eradication of your people, there's no other fate more deserving.
1 He Can Be Found In Revendreth in Shadowlands
When Kael'Thas was defeated and ultimately killed in the Magister's Terrace, his soul was deemed worthy of redemption after paying for his crimes with penance in Revendreth. He narrowly avoided being swallowed by The Maw sometime after Arthas fell in Icecrown, but nonetheless suffered a different kind of torture.
Kael'Thas was filled with sins and anima energy from others, to amplify his own abilities and his instability that lead to his power. The player must help the Venthyr redeem Kael'Thas' soul, or else condemn him to The Maw for all eternity.