You need to get Swamp Tar and take it to the chemist in Rimmington where he can turn it into oil.
Buy a tinderbox from any general store then use it with your lantern.
You can get an unlit bug lantern from any of the Slayer Masters in Runescape. You must have Level 33 Slayer to equip it and it acts as a shield and helps when fighting Harpie Bug Swarms.
Use a tinderbox on the lantern.
Use a Cut Emerald on a Bulls-Eye Lantern that doesn't have a lens.
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