The Corridor of Light is a corridor connecting the Temple of Light to the under-city under Prifddinas. The corridor was discovered during the Within the Light quest. It is partially collapsed, with access to the under-city blocked. At the end of the quest, however, Arianwyn says he will send dwarven miners to clear the blockage. This will occur for Plague's End, the last quest in the Elf quest series.
This information has been compiled as part of the update history project. Some updates may not be included - see here for how to help out!