The Three Kings #3 Blend incense, Petrus, is one of our best sellers. The main ingredient is Olibanum or Frankincense. This resin is taken from the Boswellia tree that grows on the eastern tip of Africa. The resin is dried into grains, washed and mixed with sandalwood for extra hints to smell. The finishing touches are the flower blossoms and spices that are a part of the Three King recipes.