The lens mould is a quest item used in the Observatory Quest. It is obtained by searching the goblin stove in a locked kitchen in the dungeon below the Observatory. The cell can be unlocked with the key found in one of the many chests around there. The player must give the mould to the Observatory Professor along with a piece of molten glass in order to make a new lens for the telescope. The professor will be unable to make the lens and will instead return the mould and glass to the player to make himself.