World of Warcraft: Warlords of Draenor - Fury of Hellfire

The warlock Gul’dan persuaded the Iron Horde's remaining leaders— who were enduring crushing defeats against the champions of Azeroth—to serve the Burning Legion. Their servitude, they believed, would give them one last chance to turn the tide of battle. Only Grommash Hellscream proved difficult to break, and so Gul’dan imprisoned him, hoping to make an example out of the former warchief. Gul’dan took control of Hellfire Citadel, intending to use it as a staging area for the Legion to invade

The warlock Gul’dan persuaded the Iron Horde's remaining leaders— who were enduring crushing defeats against the champions of Azeroth—to serve the Burning Legion. Their servitude, they believed, would give them one last chance to turn the tide of battle. Only Grommash Hellscream proved difficult to break, and so Gul’dan imprisoned him, hoping to make an example out of the former warchief. Gul’dan took control of Hellfire Citadel, intending to use it as a staging area for the Legion to invade Draenor. He then proceeded to summon the demon lord Archimonde. Meanwhile, the heroes of Azeroth assaulted the citadel’s gates, invading from both land and sea. Aided by Khadgar, Yrel, Durotan and a freed Grommash, Azeroth’s champions battled their way through the horrors unleashed within Hellfire Citadel. After a harrowing struggle that nearly destroyed Draenor, the heroes were able to cast down Archimonde. Yet, even as he fell, the demon hurled the treacherous Gul’dan through a portal. His pact with the Legion was far from being fulfilled.