In days long past, a powerful and ancient civilization ruled the land of the rising sun. Known as the Nilai Kanai, these people were technologically and mystically advanced, holding power over science and magic unknown before or after. Yet, there's was not a perfect society. Like the humans of today, they polluted their waters and corrupted their skies with toxins. Rather than change their ways, they chose to play at being gods, and created a being to dispose of their wastes. Known as Dagahra, this creature would consume the pollution that the Nilai Kanai produced, thus cleansing the waters. Dagahra did consume pollution, as it was constructed to, but produced a toxic side effect: bariums. Releasing thousands of the acidic sea stars from its body, Dagahra destroyed its creators, then fell into a deep slumber below the waves.

Several thousand years later, Dagahra was reawakened by a new insurgence of pollution into its domain. Awakening to fulfill its purpose once again, the toxic monster emerged from its lair, consuming man's waste and releasing its deadly spawn. Soon, the oceans ran red with its lethal sea-stars. Then, it emerged itself, spreading destruction to the land dwellers that feed it so much waste.

Yet, it was met by a powerful entity, known as Mothra Leo. Battling Leo with all of his might, Dagahra fought the noble Mothra to a standstill. Yet, when he dragged Leo below the water, the advantage was his, and he encrusted the noble warrior with his toxic spawn. As Dagahra forced his foe from the water and onto a recently revived Nilai Kanai pyramid, he closed in to finish the job. Yet, his ancient creators sought to foil him from beyond the grave, as ancient traps activated and bombarded the toxic one with bolts of rainbow lightning. Forced to retreat, Dagahra circled the pyramid, seeking a way to continue his assault on the heroic Leo.

But, just as the tide seemed in his favor, the water spirit Ghogo released his power into the damaged Mothra, reviving him and allowing Leo to rise from defeat and battle against Dagahra. This time, Dagahra was at a disadvantage, as Ghogo's magic gave Leo a powerful boost in energy, as well as the ability to follow Dagahra under the waves to continue his assault. Try as he might, Dagahra couldn't fight of the empowered Leo. Then, his foe did something startling. Splitting apart, Leo dove into Dagahra's stomach. The toxic one was wracked with agony as his enemy literally carved his internal organs apart. As his last dieing scream echoed through the depths, Leo dragged his venomous carcass from the water. Purified by the Nilai Kanai temple and Leo's combined power, Dagahra returned to seawater, and was dispersed by Leo. Thus ended the reign of the toxic beast Dagahra, the product of humanity's foolish pride.