Embuk cursed the darkness. His torch was sputtering the last of its light away and there was easily a day of travel before reaching the surface. "I have but this bejeweled ring and 100 pounds of gold and gems to light my way. Surely I will die here a fool, alone with my treasure. I wish I had a reliable lanthorn, my treasure for light!"
Suddenly there before him drifted a roiling cloud of glowing vapors within which stood a figure clad in fine silks. "Your wish is granted." The figure produced a finely crafted lamp and placed it in Embuk's hand. "It requires but a single coin to produce light. With that the figure dissolved into the smoke and was drawn again into the ring.
Embuk was overjoyed by this stroke of great fortune. "I am saved!" He placed a copper coin into a tiny slot near the base and the lamp flared into light equal to a candle. "A mere candle? Perhaps silver will brighten things."
Slipping a silver coin into the slot the lamp did indeed brighten and it was as if he had a new torch with which to see his way. Though his joy was short lived for it became low as a candle after less time than a torch would burn. "Mayhaps gold will satisfy you? he remarked to the lamp as he slid another of his many coins into the greedy lamp.
This went on for another day and Embuk did indeed escape the darkness of the caverns, but with a much lessened burden of coins. He was however richer for the lesson of misguided wish making.
The lanthorn of avarice is but one of many such treasure draining items that adventurers may discover in their travels.
Copper coins fed into it provide a candle equivilent light source for 1 turn. Silver pieces provide the equal of torchlight for 4 turns. Electrum provides torchlight for 6 turns. Gold coins provide an area of light twice the area of a standard torch for 6 turns. Platinum provides the equal of daylight at the range of two torches for 6 turns and forces a turning check for undead as if faced with a level 3 cleric, although they will not be destroyed, only kept at bay.