This is the blank area underneath all of the green, glowing graffiti on the walls ... door in the Dark Castle you have to use your pickaxe on the breakable ice to get torches.

If you've worked with Merlin to wrap up "The Forgotten Relics" quest, you'll be tackling one the darkest quests of all: "The Dark Castle ... to the note on the wall) and it will reveal the ...

To start The Dark Castle ... you'll come across a wall with a missing door. Use your camera to take a selfie with the hollow space, revealing the door. Enter to find tiki torches on the ground.