The Crystal Vice is a section of the Dragonblight filled with ice giants and jormungar. It borders Crystalsong Forest to the north. Ko'char the Unbreakable leads the giants here, and gives quests to fight the invading worms. Goblins of Nozzlerust Post can be found here as well.
Hour of Twilight
This section concerns content exclusive to Cataclysm.
It's here, the entry point from the Caverns of Time is situated and where adventurers meet up with Thrall to help escort him to the Aspects. The group, however, is quickly discovered and groups of ice elementals led by the fearsome ascendant Arcurion will try to stop the shaman from reaching the Wyrmrest Temple, the last bastion of Azeroth's defenders, which is now assaulted by Deathwing's loyal minions in order to finally bring the Hour of Twilight.
It's unknown what has become of the frost giants that once lived here.