Marrentil tar

To make Marrentill tar you need a herblore level of at least 31.

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 Marrentill

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