Japanese writer and scriptwriter. Also known as "Urobutcher" due to his many of his stories having dark and nihilistic themes and/or tragic plot twists liberally sprinkled with gory elements, such [[Fate/Zero]], [[Phantom of Inferno]], and [[Mahou Shoujo Madoka Magica]]. See post #1424416 for some examples of stories he's left his signature touch on. 

Wikipedia article: http://en.wikipedia.org/wiki/Gen_Urobuchi
虚淵玄