The location of this achievement is at the bottom of the Lost Grove (which itself is at the bottom of the Black Root Burrows) where you get the Light Burst (which is required to reach the achievement location). Once you reach the bottom where there are a few floating logs, go to the right until you reach the pressure plate that turns off the green laser above you. Use Light Burst and bounce it off the blue launch pads to destroy the blue floor up and to your left. Then go through the opening to an ability point and continue to the next pressure plate. Below and to the left of the plate is a switch that opens a door to the left of the floating logs. Once you flip it go through the now open door and after watching the memory/cutscene, the achievement will unlock.