Thunder Bats are common bats that hide in caves in Erikuria and lead a predominantly nocturnal lifestyle. Their white blood can absorb magic, heal wounds and cure diseases. This is all that was written in the diary of the demon Rakshasa, who first discovered the bats in the caves of Erikuria during one of the horned ones' forays into the lands of people.

The demon took several individuals with him and studied their blood for a long time, subjecting it to magical effects. He tested all the properties of white blood on human test subjects and himself.

One day, he tried to expose white blood to necrotic magic and ice magic at once. He gave the resulting blood to a person to drink, and the person turned into a monster that almost killed the demon. Rakshasa realized that his research was dangerous, so he tore out all the pages describing his experiments from the diary and burned them. Only a brief description of the bats themselves remained.

A few years later, the demon died, and his diary fell into the hands of human soldiers who had infiltrated the demons' territory. They understood nothing of it, so when they returned to Erikuria, they gave it to the library. A hundred years later, Amanda Nix found the diary and learned about the unusual bats. Who knows, maybe if the demon had not torn out the pages from the diary, the white blood crisis could have been avoided.