Humbaba the Terrible was a giant with the face of a lion who guarded the Cedar Forest of ancient Mesopotamian legends. The Cedar Forest was where the gods lived, and by the will (or order) of Enlil, Humbaba also terrorized humans. The Epic of Gilgamesh describes Humbaba’s roar as a flood, his mouth as death, and his breath as fire. Humbaba also had hearing excellent enough to hear things at least one hundred leagues away.
Humbaba was eventually defeated by Gilgamesh by way of trickery and deceit. When Humbaba’s head is delivered to Enlil, Enlil exacts revenge in anger and spreads Humbaba’s seven splendors (or auras) to various aspects of nature including fields, rivers, lions, and forests.
Seeing as how Humbaba is dead and his auras have been spread about the world in various forms, I wouldn’t use Humbaba as a being in direct fashion. I’d probably take an angle that a character in one of my stories would have to visit the seven different areas in which the auras were distributed and collect some aspect of those locations. For example, a character might have to collect three lion whiskers from a living beast and soak them along with a forest leaf in clean river water under the sun in the midst of an open field. Some such like that would work well for a proper quest, I think. Of course, the quest would have to be delivered in a riddle or omen to properly capture the Sumerian methods of delivering quests like this.
“Humbaba.” Wikipedia, Wikimedia Foundation, 07 Jun. 2020, en.wikipedia.org/wiki/Humbaba.