Talk:Shulva, Sanctum City/@comment-47.145.168.186-20161026061936/@comment-3236835-20161026070722

Make sure you have the Dragon Talon in your inventory and interact with the altar beyond the Rotten's boss room (Black Gulch). Since you mentioned you have the DLC, then I assume you're playing the original game with the rest of the chapters downloaded separately, in which case the key should have been automatically added to your inventory.

In Scholar of the First Sin, you first need to find the key behind the Forgotten Door in Majula's pit (I would still give a look in there just in case).