Malevolence appears as a purple, bubble-like substance that infiltrates a being such as a human, a seraph, or an animal, and, in great enough quantities, transforms the carrier into a hellion. The level of malevolence corrupting a person or vessel's body determines what type and strength the being will become and receive once transformed into a hellion. Malevolence is impurities born from the negative emotions of humanity, ultimately threatening the existence of humans and seraphim. In some locales, it is visible as a purple particle moving horizontally. Only a Shepherd and those working in concert with them, through the power of the Prime Lord seraph, have the power to purify malevolence.
All animals infected with malevolence can transform into a mythical being from inspired legends and mythology, or a more powerful and elder form. Examples include a bird transforming into a harpy or a dog into a werewolf. Important factors such as environment, lifestyle, relationship, temperature, feelings, and emotions determine the appearance of a human or seraph, unlike an animal, which will simply further evolve or mutate. There are also fixed-gender hellions. Some examples include Medusa, Echidna, and Succubus hellions, all of which can only be derived from a female human or seraph.
Malevolence in this regard is the result of a curse. When seraphim descended from the heavenly realm, wishing to live in harmony with humans, those seraphim who did not seek co-existence with humans and remained in the heavenly realm cast this curse upon the world. While humankind had always generated malevolence, it would now cause the horrible transformations described above.