Key of War

Key of War was a miscellaneous Legendary crafting material in Diablo III, and could be combined with the other three keys to create a portal device leading to one of the four realms of evil.

It can stacked up to a maximum of 5000, and is account bound.

This key could only be used to create an Infernal Machine for level 70. One such key was needed for each craft, regardless of which realm is chosen.

As of patch 2.3, it no longer drops, existing Keys are transformed into Infernal Machines of corresponding type.

Acquisition
Key of War dropped from Sokahr the Keywarden in Dahlgur Oasis at Torment difficulty, only at level 70. If it dropped, it did for every member of the party.