Azshara was known as the most beautiful of all the night elves. The Well of Eternity novel refers to her "deep, violet skin", "long, thick, lush, and moonlight silver" hair, and "artfully curved backside." She was vain and self-absorbed, and only cared about the noble Quel'dorei. But the common Kal'dorei still loved her, even though she didn't return their affection. They even renamed the capital of their nation Zin-Azshari, echoing the many dictators who named capital cities after themselves on Earth. ("I hereby rename this city Bobland!")
Like all Quel'dorei, Azshara was fascinated by the arcane magic that spewed forth from the Well of Eternity. Her top advisor, Xavius, was even more fascinated, and suggested that Azshara use the well's magic to remake the world in her own image. Awesome, so everyone's going to be a beautiful magical crackhead. It's just like L.A.! Reshaping the world is a tough job, so Xavius suggests that they find some help -- for example, this awesome guy he met in a bar that's totally into arcane magic.
Xavius set up a meeting between Azshara and Sargeras, in which the former told the latter that she wanted to "cleanse the world of lesser races." There weren't a whole lot of lesser races around then, were there? Mostly dragons, furbolgs and tauren. Azshara was quickly entranced by the demon lord, so when Sargeras asked that she open a portal using the energies of the Well of Eternity, she did so without hesitation. And that's how the Burning Legion first set foot on Azeroth.
The portal was big enough to let some of the Legion's commanders and shock troopers through, but Sargeras himself was still stuck in the great dark void. The Legion stormed through the night elf cities, slaughtering and burning while Azshara laughed in her city. Incredibly, most of the night elves were STILL loyal to her and believed that she was a captive of the demons -- all except a small resistance, who came to suspect that she had been corrupted. Gee, what was their first clue? The demonic rampage or the hysterical laughter?
Anyway, the leaders of this resistance -- who you will DEFINITELY know as Malfurion Stormrage, Tyrande Whisperwind, and Illidan Stormrage -- got together with the demigod Cenarius and a bunch of dragons and came up with a plan to fight back. They gathered the non-noble Kal'dorei, and under the command of the elf Lord Ravencrest, they started kicking some serious demon behind. Sargeras was incensed at this and sent his top commander, Archimonde the Defiler, through the portal to Azeroth. Around that time, Azshara told Lord Xavius to kick all non-Highborne out of the Well of Eternity so they could use it to summon Sargeras himself. Azshara kind of had a thing for Sargeras, believing him to be the only male worthy of her beauty. Ew.
The resistance fought all the way up to the gates of Zin'Azshari, hoping to "free" Azshara from her "capitivity", but they were stopped in their tracks by Archimonde. Archimonde had hidden eredar warlocks in the clouds and rained hellfire and destruction upon the night elf resistance. Then Archimonde told them to stop using Rain of Fire and just dot up the elves, which everyone agreed was a lot more effective. The night elves went to the general forums to complain, but got hit by Curse of Exhaustion and died, forgotten, in Raids and Dungeons.
While the two sides battled, Malfurion realized that the only way to end this was to ... say it with me, Blow Up The World. This angered Illidan, who was all emo about Tyrande liking his brother better and pissed off about possibly losing his source of magic. He spitefully set off to warn Azshara about Malfurion's plan. (Note: This is the official WoW version. In the alternate universe War of the Ancients Trilogy world, Illidan is a lot nicer and doesn't warn Azshara, the Well is destroyed accidentally, and a time-traveling orc hits Sargeras with an axe. As a strong believer in alternate universes being a cheap cop-out, I'm going with the original here. If you want to know the full alternate version, prepare to blow about twenty-five bucks on the WotA trilogy.)
When Furion and company came a-knockin', Azshara's folks were ready for them. While they continued to try to summon Sargeras, Azshara and her guards were able to severely injure Tyrande, which sent Malfurion into a blinding rage. Azshara and Malfurion spellcasted it out, arcane vs. nature, mage vs. druid. In-between the Wraths and Arcane Missiles, Illidan (who was on injured reserve for the battle) snuck up to the Well and grabbed a bunch of vials for later
freebasing use. Ah, Illidan. You're an untrustworthy, half-demon magic addict, and that's why all the ladies love you.
The magic that was being so carelessly flung around by Azshara was actually helping Malfurion. The arcane energy destablized the portal that was being opened for Sargeras and blew up the entire well. Most of the sentient beings saved themselves by clinging onto debris, but Azshara and her Highborne were sucked down into the swirling Maelstrom. Azshara cast a bubble of protective magic over herself, but before she died, she heard a voice promising her power untold in return for future services. As her bubble wore off and Forebearance kicked in, she transformed into a hideous naga. Well, that's what it says. I think she's actually pretty attractive for someone with octopus legs. Her Highborne servants also became naga, and vowed to continue wandering aimlessly around beaches until aggroed by questers.
Where she is now: Azshara still rules her Highborne in her castle at Nazjatar, deep below the Great Sea. As expected, she is quite unhappy with what the Kal'dorei have become, and is constantly plotting her revenge against the current night elf leadership. She's probably pretty chill with the blood elves, though. Modern-day Azshara features the ruins of Zin-Azshari, and is considered cursed by the night elves.
Personal characteristics: She now has five octupus legs, four arms, and a head full of snakes, once again proving that Blizzard really enjoys ripping off Greek mythology. According to Blizzard's RPG manual Shadows and Light, she's about twenty feet long these days and draped in jewels brought to her by adoring naga. She's apparently still very good at manipulating people and continues to have a crush on Sargeras. Why would ANYONE have a crush on Sargeras? Does he even have a physical body? And how would that work with the octupus tentacles?
For more information: Queen Azshara on WoWWiki, War of the Ancients on worldofwarcraft.com, the alternate history of War of the Ancients on WoWWiki