American science fiction author and painter most well known for his fantasy guides to extraterrestrials and demonology.
He painted over three hundred covers for books and magazines, including Life Magazine, Time, and Newsweek.
He also did character designs for movies, including Harry Potter and the Goblet of Fire, Blade II, John Carter, and The Hobbit.
He married Laura Hansen Barlowe in 2013. He also had two daughters.
He created character designs for Hellboy, which starred Ron Perlman.