Buy OSRS Swamp tar
Swamp tar is a thick, foul smelling substance in Old School RuneScape. It is a members item that stacks in your inventory and can be traded with other players. It cannot be crafted, and no shop sells it, so buying it saves a lot of time.
Swamp tar has many uses. Mix it with flour and heat it on a fire to make swamp paste. Swamp paste is used for repairs, the Sea Slug quest, and the Shades of Mort'ton and Fishing Trawler minigames. You can also combine swamp tar with guam, marrentill, tarromin, harralander, or irit leaves to make herb tar. Herb tar is the ammo for salamanders, and one herb makes 15 tar. Making herb tar can also be used for tick manipulation to do some actions faster. Swamp tar can even be turned into lamp oil, which fills lanterns so they can be lit.
Swamp tar shows up in many quests, such as Cold War, Eagles' Peak, Horror from the Deep, Lunar Diplomacy, and Troll Romance. Getting it yourself means killing Cave Slimes or picking it up in the swamps. Buying a stack lets you skip that grind.