Location: Source Temple
Miss-Able: No (Main Story Quest)
Once in the source temple you can explore the initial area for progress in some quest lines, particularly near the broken mirror.
Afterwards, go to the northern path in the cave and find a large boulder/cave-in. Locate a small switch to left of it on the wall to make it disappear. Continue onward through the new tunnel to find a new waypoint shrine.
The puzzle presented by this room is entirely optional, you can skip it.
Walk to the furthest north room, it contains a circle of candles on the ground.
To open the door and unlock the achievement do the following.
1. Light each of the outside candles, wait a few moments for a lightning strike.
2. Light only the centermost candle, wait a few moments for a lightning strike.
3. Light the West, Center, and East candle.
Next Story Achievement: