It’s rather easy to overlook the fairy location in Tunic’s Eastern Vault location. If you warp your way there, head straight south and down the main staircase. Go west until you reach the room with all the custodians in it. Once you’ve dispatched them and have some privacy to solve puzzles, it’s time to get to work.
Move your attention to the energy node that you activated your first time here. Now, it’s just a grey square on the floor.
Take note of the candles around the node. If you’ve done the tree puzzle for a fairy in Western Garden or the fountain puzzle in the Overworld, the solution will be familiar. However, if you haven’t, take note of how many candles belong to each cluster. One and Four on the right side, three at the bottom, and so on. You need to count up each cluster of candles with your Holy Cross (D-pad on a controller, arrow keys on a keyboard). So, you press right first, because it has the cluster of one candle. The left would be second because it has a cluster of two candles. And then you continue in that pattern.
Still not working for you? Here’s the solution: Right, left, down, right, up, left.
As a reminder, if you’re having trouble finding the location, pressing up, left, up, right, down, right on the “Holy Cross” will send three sparkles out that move in the direction of the fairy.
