"There are many types of monsters in this world. Monsters who will not show themselves or who cause trouble. Monsters who abduct children, monsters who devour dreams, monsters who suck blood, and monsters who always tells lies. Lying monsters are a real nuisance; they are much more cunning than other monsters. They pose as humans even though they have no understanding of the human heart; they eat even though they've never experienced hunger. They study even though they have no interest in academics; they seek friendship even though they do not know how to love. If I were to encounter such a monster, I would likely be eaten by it...because in truth, I am that monster." - L, Death Note Rewrite 2: L's Successors.

Every child has monsters. You may have had the Boogie Man, or a monster under the bed. They screw up your life, terrify you… until you turn six, and grow out of your fears. It appears that we geniuses have… different monsters. They last longer. L believed that HE was the monster, and Near`s sinister being was the thought of never being needed by anyone, being forgotten in the shadows. Mine was…slightly more childish. He was green and cruel and hated the thought of anyone being better than him. The thing, you see, about the monsters of such brilliance, is that they never go away, and affect their hosts greatly. The fears they place are much more rational (too rational to be easily forgotten) and torture their hosts until the day they die. I happen to be dead now, and it`s true; my monster seems rather pointless and overbearing now. It got to the point where he changed my entire outlook on life. In a sense, you could say that I became my monster. My monster was green, and cruel, and hated the thought of anyone being better than him. He was envy.