Following the establishment of the city-state of Dalaran, the magocrats formed the Kirin Tor as a specialized sect that was charged with cataloging and researching every spell, artifact, and magic item known to mankind at the time.
The Kirin Tor became the city’s ruling power. The Kirin Tor’s headquarters was the Violet Citadel, an impressive building so named for its stone walls which gave off a faint violet light. The ruling council, six members in all, met in the Chamber of the Air, a room with no visible walls — the gray stone floor with its central diamond symbol stood beneath an open sky that shifted and changed rapidly, as if the time sped past within the chamber.
Even the Kirin Tor, however, found itself powerless to stop Prince Arthas and his forces when he led the Scourge through Lordaeron. Arthas acquired the spellbook of Medivh and Kel'Thuzad used it to summon Archimonde, who destroyed Dalaran. The city was left in ruins. Some felt the devastation was well-deserved, since Kel’Thuzad had himself been one of the Kirin Tor (before he left to form the Scholomance). Since Kel’Thuzad was responsible for creating the Plague of Undeath and releasing the Scourge upon the world, many felt the Kirin Tor should share in the blame and the consequences.
The Kirin Tor refused to abandon their home, however. They returned to the ruins months later, destroying those few undead creatures that remained, and reclaimed their city. They erected a glowing dome around the entire city, powerful enough to destroy anyone who touches it, while they worked to rebuild their fallen city.
Eventually, the mages were able to lift the whole city from its site, leaving only a crater in its place. The Kirin Tor decided to move their floating city to Northrend, where they still rule over the reconstructed Dalaran.