Guam tar

Guam Tar can be made by doing the following steps:
 * Get Swamp tar (For example at Lumbridge Swamp or Mort Myre swamp)
 * Get a Pestle and Mortar
 * Get a guam leaf

If you've got all these in your inventory, use the Guam leaf with the swamp tar, and voila. You'll get 15 guam tar for every guam leaf.