The Halls of Lightning is a five-man wing of Ulduar in the Storm Peaks.
The Halls of Lightning is located in the eastern part of the enormous titan city of Ulduar. Here the treacherous Loken — a fallen servant of the Pantheon and former prime sentinel — mass-produced iron vrykul on behalf of his dark master's sinister plans. Loken himself guided his forces from his throne, guarded by storm elementals and fire elementals with his most powerful servants and commanders near his side. It is here that he made his last stand, before being defeated by the adventurers.[1]
The reasons for Loken's treachery and the fate of the other guardians remain a mystery, but there have been whispers of a great evil at work behind the fall of the titan city. For any heroes brave enough to seek out the truth, it lies within the corridors of the ancient compound. Thus far, however, few have braved the perils of Ulduar and returned to tell of their discoveries.[2]
Adventure Guide
Upon departing Azeroth, the titans entrusted loyal protectors with safeguarding Ulduar, an enigmatic city nestled in the mountains of the Storm Peaks. Designated supreme among his brethren was the guardian known as Loken, but with the power of the titan complex in his hands, he turned to darkness and plunged the region into chaos.
Iron vrykul
Iron dwarf
Air elemental
Earth elemental
Fire revenant
Loken
Map of the Halls of Lightning - First level.
Map of the Halls of Lightning - Second level.
Air elementals
Air revenants
Beetles (critters)
Fire giant (one, Volkhan)
Fire revenants
Molten golems
Iron giants
Lava elementals
Sparks
Steam elementals
Titanic watcher (one, Loken)
[Halls of Lightning]
[Heroic: Halls of Lightning]
[Shatter Resistant]
[Timely Death]
[20-30D] Whatever it Takes!
Patch 7.3.5 (2018-01-16): Level scaling implemented, previous instance level: 79 - 80. 
Patch 6.2.0 (2015-06-23): New Timewalking difficulty added. 
Patch 3.0.2 (2008-10-14): Added. 
World of Strats Halls of Lightning instance guide
