House Key is a Key item in Dark Souls 2.
- From the Cardinal Tower bonfire in the Forest of Fallen Giants, go to the area where you climb a big tree root/branch across scaffolding.
- Drop from the branch onto the rooftops below
- Jump from house scaffolding to scaffolding with archer
- Walk through cave entrance, stop and wait for boulder to pass
- Talk to the nearby NPC, called Cale the Cartographer until he gives you the key.