Oil lamp
From Wikihack
An oil lamp, cost 10, is a light source. Applying one will provide light to darkened areas for 1000 to 1499 turns. They can be refilled with scrolls of charging or potions of oil (using the #dip command). If you dip a lit oil lamp into a potion of oil, you are likely to cause a fireball.
When you release a djinni from a magic lamp, the lamp becomes an oil lamp.
If an oil lamp is cursed, it might not light when applied.
