Lurking beneath the lands of Sollgel, a huge arachnid lived. Standing much taller than a human being, the spider only came out from beneath the earth to feed every few months. However, during a scrap involving Minilla and a Kamacuras, a stray fallen rock awoke the mammoth sized killer. Rising from the ground, casting off the layers of thick earth, the massive spider attacked the first being it saw, being Riko and Goro. Running, and climbing the mountainside, the pair managed to escape the titan's wrath. Soon, however, the animal moved to the toward the human's new base, located in a cave below the Earth, and once again tried to feed. Having their backs against the wall, the terrified men managed to avoid the grabbing claw of Kumonga, leaving the spider's hunger to rage still.
It wasn't until Minilla strayed by did the devil have a chance for a meal. Springing from the tree cover, the spider cocooned the hapless young monster in a thick web. As he was about to move in for the kill, a Kamacuras revealed itself, and tried to fly by the scene, but Kumonga would not let it pass, and cocooned the armored insect. Staving the feel for nutrition, the animal injected its deadly venom into the prone insect, killing it instantly. Kumonga then moved on, about to do the same with Minilla, until Godzilla intervened. Throwing a rock, the monster battled the spider back. A long battle ensued, but in the end, Godzilla and Minilla set aflame the black body of Kumonga. Surviving the wicked battle, the Japanese sought to remove the animal, while in its weakened state, to Monster Land.
There, the creature was among the precipitants that the Kilaakian controlled when they invaded. Though humanity was able to sever the link, and send the spider into battle with King Ghidorah, alongside a host of Earth's monsters. Triumphing over the golden space dragon, Kumonga was returned to Monster Land where it lives to this day.
One of the many monsters called forth by the Xilien in their campaign to conquer Earth. Kumonga's genetic structure contains a gene called M-Base, the same gene found in the Xilien and their genetic offspring and what allows the alien invaders to control the monsters.
Bent to the Xiliens' will, Kumonga first attacks a trailer park in Arizona as part of a global-wide assault from the monsters Rodan, Anguirus, King Caesar, Zilla, Kamacuras, and Ebirah. As quickly as Kumonga appeared, though, the creature is teleported away by his alien masters. Using the disappearance of the monsters as a sign of loyalty between the Xilien and humanity, who have yet to learn of the alien invader's true intent, the Xilien move to phase two of their plan as they warn against an incoming star known as Gorath, which is on a collision course with Earth. However, the Xiliens' true intent is quickly discovered, along with their ability to control those that possess the M-Base gene. Their old plan in ruins and their leader now dead, the Xiliens' forgo a more peaceful approach to the invasion and instead unleash a full scale attack combining the might of their own fleet of ships with that of the controlled kaiju. This approach appears successful, until the Gotengo releases Godzilla from his artic prison.
Seeking a rematch with the flying battleship that sealed him away almost 40 years ago, Godzilla chases after the Gotengo, as the Xiliens' send monster after monster to try and defeat the nuclear giant. Finally, Godzilla arrives in New Guinea where he is challenged by Kumonga, who leaps around the King of the Monsters firing webbing at the behemoth. However, Godzilla catches on fast, and instead reacts by grabbing one of the creature's strands of webbing before it can materialize into a net. With the creature's webbing in hand, Godzilla begins to swing the still attached Kumonga around in circles before releasing, sending the giant spider flying off into the distance.