Viromancy

Viromancy is a sub-school of magic that sits at the intersection of Transmutation and Abjuration. Viromancy studies viruses using magic to design, alter and enhance the diseases to serve the caster. Through Viromancy viruses can be made to drain life into their creator, subsume their will or be made entirely invisible until activated by their creator.
An example of a disease created by Viromacny was the Olfen Plague which was designed by the Ash Elves to devastate southern Teremia and open the way to its annexation.