From WoWWiki

Fallen Sky Ridge is a widestretched area of northwestern Hellfire Peninsula populated by dangerous colossi. Its most prominent feature is an enormous red crystal which curiously plummeted from the sky.

Spoiler Alert! The following reveals major plot details from the Warcraft series ... read at your own risk!

The truth is that the crystal was purposefully planted into the earth in order to corrupt and summon the colossi with its inherent essence. The blood elves are behind this scheme, with Prince Kael'thas being the ultimate mastermind and culprit.

Subzones of Hellfire Peninsula

The Abyssal Shelf • Broken Hill • Cenarion Post • Den of Haal'esh • Dustquill Ravine • East Supply Caravan • Expedition Armory • Expedition Point • Falcon Watch • Fallen Sky Ridge • Felspark Ravine • Forge Camp: Mageddon • Forge Camp: Rage • Gor'gaz Outpost • The Great Fissure • Haal'eshi Gorge • Hellfire Basin • Hellfire Citadel • Honor Hold • Honor Hold Mine • Invasion Point: Annihilator • The Legion Front • Mag'har Grounds • Mag'har Post • Northern Rampart • The Overlook • The Path of Anguish • The Path of Glory • Pools of Aggonar • Razorthorn Trail • Reaver's Fall • Ruins of Sha'naar • Sha'naari Wastes • Shatter Point • Southern Rampart • Spinebreaker Mountains • Spinebreaker Pass • Spinebreaker Post • The Stadium • The Stair of Destiny • Stonewall Canyon • Supply Caravan • Temple of Telhamat • Thornfang Hill • Thrallmar • Thrallmar Mine • Throne of Kil'jaeden • Valley of Bones • Void Ridge • The Warp Fields • Zeppelin Crash • Zeth'Gor