Those now known as blood elves were once high elves. In the transition that led to this renaming, they glorified their civilization while discarding their honor. Life for the blood elves changed during the Third War, when King Arthas' Scourge sacked Quel'Thalas and shattered the elven race. The Scourge slew more than 90% of the high elven population, devastating their culture. Prince Kael'thas Sunstrider was studying magic in Dalaran at the time of the disaster. He returned from his studies to find Quel'Thalas in ruins. Thirsting for vengeance, Kael'thas gathered the survivors and renamed them "blood elves" in honor of their fallen kin. Prior to the Sunwell's destruction, all high elves were constantly bathed in its magical power. Now bereft of this arcane energy, the blood elves (and high elves) suffered from their withdrawals. Kael'thas claimed that they would soon die without another magical source to replace the Sunwell. The blood elves therefore set about learning to drain magic from alternative sources.
Soon, the blood elves clashed with the Scourge and the Amani trolls, who were making inroads into former elven territory. The blood elves defended their homeland, and, eventually, having reestablished a degree of safety to their land and prevented their society from degenerating, Kael'thas left his homeland. He took a group of the strongest blood elf warriors and spell casters and joined the Alliance against the Scourge. They were eager to avenge themselves on the undead forces; however, bigotry prevented the human forces from seeing the aid the blood elves could bring to their fight. Due to those human prejudices, Kael'thas was forced to accept the assistance of the naga queen's servant, Lady Vashj, and the reptilian naga. When the humans discovered that the blood elves were working with the naga, they were imprisoned and sentenced to death by the racist human Grand Marshall Garithos (who had commanded the New Alliance). The blood elves who sided themselves with Kael'thas escaped with the aid of the naga, fled to Outland, and joined Illidan Stormrage's forces. This group of blood elves then helped defeat the demon Magtheridon and claimed his Black Citadel as their own.
In exchange for the blood elves' loyal service, Illidan gave them a place to live, as well as further techniques to siphon mana from anything with arcane power. Blood elves in Outland now hunt demons and feed off the demons' magic. As a consequence, despite what other races might suspect, blood elves are hardly on friendly terms with demons. Indeed, blood elves view demons with abhorrence as well. Even blood elf warlocks believe demons are useful tools, not potential allies. Not every blood elf lives in Outland. Most blood elves still live in Azeroth, particularly in Quel'Thalas. These blood elves seek to reclaim their lost homeland and destroy the Scourge at any cost A lone representative, Rommath, was sent back to Azeroth with a message of hope for the blood elves remaining in Quel'Thalas: That one day Kael'thas would return to lead his people to paradise. Rommath has made great progress in teaching the blood elves advanced techniques to manipulate arcane energies. With renewed purpose, the blood elves have now rebuilt the city of Silvermoon, though it is powered by volatile magics. Emboldened by the promise of Kael'thas' return, the weary citizens of Quel'Thalas now focus on regaining their strength, even as they forge a new path into an uncertain future. While they despise most other races, they have come to accept that the Forsaken are different, or at least share the same goals as the blood elves. The blood elves in Outland do not give the Alliance or the Horde much thought. They are busy seeking power and honing their abilities.
Blood Elf Info from http://www.wowwiki.com/Blood_elf
Soon, the blood elves clashed with the Scourge and the Amani trolls, who were making inroads into former elven territory. The blood elves defended their homeland, and, eventually, having reestablished a degree of safety to their land and prevented their society from degenerating, Kael'thas left his homeland. He took a group of the strongest blood elf warriors and spell casters and joined the Alliance against the Scourge. They were eager to avenge themselves on the undead forces; however, bigotry prevented the human forces from seeing the aid the blood elves could bring to their fight. Due to those human prejudices, Kael'thas was forced to accept the assistance of the naga queen's servant, Lady Vashj, and the reptilian naga. When the humans discovered that the blood elves were working with the naga, they were imprisoned and sentenced to death by the racist human Grand Marshall Garithos (who had commanded the New Alliance). The blood elves who sided themselves with Kael'thas escaped with the aid of the naga, fled to Outland, and joined Illidan Stormrage's forces. This group of blood elves then helped defeat the demon Magtheridon and claimed his Black Citadel as their own.
In exchange for the blood elves' loyal service, Illidan gave them a place to live, as well as further techniques to siphon mana from anything with arcane power. Blood elves in Outland now hunt demons and feed off the demons' magic. As a consequence, despite what other races might suspect, blood elves are hardly on friendly terms with demons. Indeed, blood elves view demons with abhorrence as well. Even blood elf warlocks believe demons are useful tools, not potential allies. Not every blood elf lives in Outland. Most blood elves still live in Azeroth, particularly in Quel'Thalas. These blood elves seek to reclaim their lost homeland and destroy the Scourge at any cost A lone representative, Rommath, was sent back to Azeroth with a message of hope for the blood elves remaining in Quel'Thalas: That one day Kael'thas would return to lead his people to paradise. Rommath has made great progress in teaching the blood elves advanced techniques to manipulate arcane energies. With renewed purpose, the blood elves have now rebuilt the city of Silvermoon, though it is powered by volatile magics. Emboldened by the promise of Kael'thas' return, the weary citizens of Quel'Thalas now focus on regaining their strength, even as they forge a new path into an uncertain future. While they despise most other races, they have come to accept that the Forsaken are different, or at least share the same goals as the blood elves. The blood elves in Outland do not give the Alliance or the Horde much thought. They are busy seeking power and honing their abilities.
Blood Elf Info from http://www.wowwiki.com/Blood_elf
. did ya go to Blizzcon? 
They played Nyan cat 
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