Tree Spirit Backflow Incense Tower 19cm Incense Burner £30.00 New stock arriving soon. Tree Spirit Backflow Incense Tower 19cm A Tree Spirit, Ent, or Green Man, themed Incense Tower. For use with Backflow Incense. Backflow Incense is specially designed for incense burners that have a reservoir to channel the smoke. It pours down the incense tower with dramatic effects. Backflow incense cones are specially designed, they are cones that create a thicker smoke that cascades down from the cone rather than rising like traditional incense cones.