Key of Bones

Key of Bones 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 was chosen.

Acquisition
Key of Bones dropped from Odeg the Keywarden in Fields of Misery at Torment difficulty, only at level 70. If it dropped, it did for every member of the party.

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