This area begins as a simple snowy basin, a frozen pond and an abandoned mine in an unremarkable area of southern Frostfire Ridge. After the Horde expedition (consisting of the player, Khadgar, Thrall, Drek'Thar, Ga'nar, etc.) have finished the Assault on the Dark Portal scenario, their stolen Iron Horde ship is beached on the southern shores of Frostfire Ridge. They are promptly met by Durotan, who knows of their plight and gifts the plateau of Frostwall to the player to use as a base for their expedition.
Conversion into an Horde Garrison
Khadgar creates a portal and Gazlowe comes through with workers to start building the garrison. Once an Horde player has completed the prerequisite quests, they establish a level 1 garrison in the area. This small town consists of some palisade walls and a few scattered huts and tents. From this point forward, when the player enters the plateau, they are greeted with text defining the area as "Frostwall <Player>'s Fort". When the garrison is upgraded, it becomes known as "Frostwall <Player>'s Garrison"
More in-depth information concerning the garrison can be found in the Garrison article.