Humbaba was a beast of the gods that lived as the guardian of the Cedar Forest, befriending Enkidu while he still lived in the wild. Enkidu made it a garden by bending the laws of the earth, and it wore a circlet of flowers on its head taken from the garden. Later after Enkidu gained humanity and befriended Gilgamesh, they both traveled to the forest to slay it. Although he cared not for the people currently suffering under his reign at the time, Gilgamesh considered Humbaba an evil of the earth that was necessary to defeat to keep the people from starvation. Enkidu wondered why it wore the circlet, and Gilgamesh replied, "For its innocent heart was it was all the more joyous for a simple wreath." As Gilgamesh returned to Uruk, Enkidu left a second circlet behind for his friend.
Humbaba wore a circlet of small, pale flowers on its head. The "Fate/Zero Animation Visual Guide I" has a portrayal of the battle between Humbaba, Gilgamesh, and Enkidu in the "Legends of Heroes" section. As with the other images in that section, it may not reflect the character's actual design.
Although a monster, Humbaba possessed the innocent heart of a young girl. It found great joy in the circlet of flowers from the garden made by Enkidu.
Nasu makes an aside on his blog pondering if the runaway Ibaraki-douji may have actually been holding back the resurrected sacred beast Death Huwawa (デスフワワ, Desu Fuwawa?) from joining the war in the Babylon Order.
Humbaba is said to have possessed claws sharper than anything on earth, surpassing even Enkidu. It required the combined might of Gilgamesh and Enkidu to defeat it.