Greater Rift Keystone

A Greater Rift Keystone (GRK) is required to open a Greater Rift when applied to a Nephalem Obelisk. They drop from level 70 Rift Guardians in normal Nephalem Rifts. On higher difficulties, two or even three Keystones may drop at once.

The GRK is lost when used. Even if player beats the Greater Rift in time, they will be forced to find a new GRK.

To participate in the Greater Rift run, every player must contribute a GRK.

Greater Rift Keystones are not unique; players may stack as many of them as desired. Drop chance increases with difficulty, from 100% to get one at Torment I, with increasing chances to get two (until guaranteed at Torment XI), and an increasing chance to get three after that.

As of patch 2.6.4, they are stored in the Materials tab.

As of patch 2.6.6, Cain's Destiny set, when completed, adds a 25% chance on any GRK drop to receive a second one.

Development
Originally, prior to patch 2.3, Greater Rift Keystones were a Legendary variant of the Rift Keystone Fragments. The rank of the Greater Rift was equal to the level of the GRK used, and this number was displayed both in the description and on the item's icon.

Getting a GRK required players to obtain the Keystone of Trials from any Rift Guardian in a regular Nephalem Rift first, then complete the Realm of Trials. Doing so would grant a GRK with rank proportional to the number of waves cleared.

Urshi originally gave players a choice of either upgrading Legendary Gems OR giving them a new Keystone with increased rank (provided players managed to beat the Rift in time).

This mysterious artifact was once used by the nephalem to prove their worth.