The book titled, Corruption, exposed Blake to a term that was foreign to most of the human race but extremely important.
From the onset of creation, the term corruption didn't exist as the Mother-stream only controlled life and death. However, all that ended during Valerius' betrayal of the realm, which led to the opening of the barrier.
With the troops of Neons that managed to make it into the universe, came Pure evil known as Anti-life or corruption; whichever one wished to call it. The worst part of the situation was that even when the Neons were dealt with, the corruption remained. Although it is actively being restricted from spreading by the Mother-stream it still manages to infiltrate multiple areas and infect things unfortunate enough to encounter it.