'I have an idea about the mirrors, but I am not sure that I'm on the right path. You have surely noticed how many varieties of crystal are present throughout Khazad-dûm; I have a feeling that some might actually react to reflected light if it comes from these mirrors.

'You see this pedestal fragment? I had assumed that it must belong to a statue or monument, until I noticed how similar its markings were to those on the mirrors' mountings. And look here: the remnant of an embedded crystal-shard.

'I noticed various crystals in several nearby areas, of different colours. Kindly fetch me four different samples. Here, let me give you a case in which to carry them, or they might break. I know how rough-and-tumble you adventurers tend to be. There was one colour prevalent in an area that has since been occupied by insects, near a ledge with a magnificent view, and some near the mining area itself.'