The Arreat Summit is the peak of Mt Arreat and the location of both The Ancients and the entrance to the Worldstone Keep. Reaching it requires navigating through numerous frozen tunnels carved long ago into the mountains by the Barbarians. Before being allowed entrance into the Worldstone Keep, any traveler must first face the Ancients on the Arreat Summit in combat. Only by defeating the three guardians can any adventurer prove their worth and gain entrance. The sole exception to this rule is the Relic of the Ancients, which allows anyone to enter the Keep without facing the Ancients.

At the center of the summit area is the Altar of the Heavens - when touched, it will awaken the three guardians so that they may challenge the one who seeks to enter the Worldstone Keep.

Arreat Summit, along with Arcane Sanctuary and Canyon of the Magi, is one of the two locations in the game where video Perspective does not work. This is because Perspective requires two layers to work with, one usually being the ground and the other for the objects that move relatively to it, but Arreat Summit has one layer reserved for the background that shows the areas below the peak.

"The Arreat Summit" is also the name of a section of Battle.net, which acts as an official guide for Diablo II: Lord of Destruction (the expansion set).