The enormous, cave-dwelling predatory arachnid known as the Beast in the Mouth of the Mountain was how the Ewok people referred to it. This creature possessed six eyes, six legs, and a collection of tentacle-like structures extending from its face. A particular specimen made its home inside a vast, cavernous area within a mountain located on the forest moon of Endor around 19 BBY. This massive arachnid was responsible for the destruction of several B1-series battle droids and the unexplained disappearance of a clone scouting squad, as it had consumed the troopers' remains.
During the subsequent investigation, Jedi General and Master Aayla Secura, puzzled by the missing troopers, encountered a local Ewok tribe that had knowledge of the creature. The Ewok chief recounted to Secura what had happened to her missing squad, including the appearance of the Beast, and requested that the Jedi eliminate the creature. Accompanied by Ewoks to the foot of the arachnid's mountain, Secura ascended the cliff face and discovered the creature's den, which was covered with the skeletal remains of her clones and other organisms. The Beast emerged and attempted to surprise Secura, destroying her battle droid companion in the process. However, the Jedi Master managed to outwit the Beast by leaping into the air and severing overhead stalactites, which then fell and fatally pierced the creature. Secura then departed, with her victory being commemorated in Ewok tribal artwork.
The Beast in the Mouth of the Mountain was an arachnoid type of being characterized by its impressive size and weight. Its body was segmented, featuring an abdominal section and a head section, connected by a neck. The abdomen had a flattened dome shape, displaying a dark green, scaly underside and a lighter-colored, ridged exoskeleton on its upper side. At its rear, there were two spinnerets or similar protrusions. For movement, it used six legs, each divided into three parts and ending in four claws.
The creature's head was mostly cylindrical, marked with spots of different colors, and topped with horn-like extensions at its upper end. It had six eyes that were reddish or orange in color. A cavity was present at the lower part of the head, from which several tentacle-like appendages hung. The creature's hide was resistant to blaster weaponry, and it possessed pink blood.
The Beast in the Mouth of the Mountain, which lived on the forest moon of Endor, was a carnivorous predator that the local Ewoks feared due to their awareness of its existence. Although it primarily stayed in a cave within a mountain, the Beast was known to leave its lair to prey on smaller creatures, including clone troopers, who were the organic soldiers of the Galactic Republic. However, it seemed unable or unwilling to consume the non-organic parts of droids. When attacking, the creature would strike with its clawed legs. After killing its prey, it would remove the body from any coverings, such as clone armor, and take it back to its lair to eat. Many creatures fell victim to this tactic, including large craniates, as evidenced by the various skeletal remains found on the floor of its lair.
By approximately 19 BBY, the Beast in the Mouth of the Mountain had taken up residence in a large cave on Endor, surrounded by a mountain and numerous stalactites and stalagmites. The native Ewoks knew about the Beast, identified the location of the huge arthropod's lair, and gave the creature its only known name.
Around 19 BBY, two warring galactic factions—the Republic and the Confederacy of Independent Systems—sent troops to the forested world. Specifically, a Republic squad was dispatched to gather intelligence on a small Separatist outpost that had been established on the moon. After the clones arrived, the Beast emerged from its lair and encountered the opposing forces, indiscriminately attacking both groups and leaving only one battle droid survivor. The enormous arachnid then took the clones, leaving behind most of their armor and the damaged droids, and returned to its lair to feed.
The Grand Army of the Republic responded to the disappearance of its scout squad by launching an investigation led by Jedi General Aayla Secura and her 327th Star Corps. Upon landing on the moon with Clone marshal commander CC-5052, also known as "Bly," the team discovered the abandoned Separatist base, which was surrounded by scattered droid parts and broken clone armor. Secura went into the forest to gather more information, where she found the lone, somewhat peculiar, battle droid survivor. However, she was unable to communicate with the droid because she was captured by local Ewoks, who took the Jedi to their village. There, the Ewok chief explained the Beast's oppressive predatory behavior to Secura, with the battle droid translating their native language, and tasked her with killing the reclusive hexapod.
Secura implicitly agreed and was guided by the Ewoks to the Beast's mountain, where she climbed a cliff face to reach an opening in its rocky surface. There, she found the Beast's refuge, a cavernous space where the floor was barely visible due to the piles of assorted bones, ribcages, skulls, and clone armor. The Beast soon revealed itself to Secura and began to strike at her fiercely with its clawed legs. One of these strikes destroyed Secura's battle droid companion; the Jedi responded by cutting through its facial appendages with her lightsaber. The Beast then made a final strike at Secura, which propelled her backward. The Jedi recovered and jumped above the creature, slicing through the stalactites above. The sharp-edged rock formations fell onto the creature and pierced its abdomen, bringing an end to the Beast in the Mouth of the Mountain.
As Secura departed, the Ewok chief created a mural to commemorate the encounter, depicting the Beast's death at the hands of the Jedi Master.
The Beast in the Mouth of the Mountain is featured in What Goes Up..., a story from Star Wars: Clone Wars Adventures Volume 5, the fifth installment in the graphic novel series of the same name. The story was penned by the Fillbach Brothers, lettered by Michael David Thomas, and illustrated by Lee Evandon. Dark Horse Comics published it on April 26, 2006.