The deployment of the Flood Disaster by the Secret Tower required the use of a special item called a Cooling Insect Nest.
The Cooling Insect Nests, made by the Engineering Worms of the Dark Domain Insect Clan, varied in size from a diameter of 50 centimeters to 5 meters. Because spatial technology was applied in the production process, even the smallest, 50-centimeter models could store a hundred thousand Ordinary Insects and a hundred Adult Insects. Throwing one of the largest Cooling Insect Nests onto a surface civilization on the level of Ulysses would result in a ruthless slaughter.
Although the Secret Tower's fleet did not carry the largest Cooling Insect Nests this time, it did bring over a hundred medium-sized ones. Those were enough for them to launch a Flood Disaster on the scale of hundreds of millions.
Don't underestimate the number one billion.