Lord Zetta is in his own words, "the most badass freakin' Overlord in the cosmos". Though not too bright, Zetta makes up for his shortcomings with sheer power and attitude.
After discovering a Sacred Tome Zetta finds a passage claiming that his own stupidity would be the downfall of his Netherworld. Infuriated, he burns the book, only to remember immediately afterwards that destroying the book would destroy his world. He quickly responds by confining his soul to the Sacred Tome and ventures to rewrite his world into existence by having the other Overlords of Netherworlds write wishes within his pages.
Source: Wikipedia, "Makai Kingdom: Chronicles of the Sacred Tome," available under the CC-BY-SA License.