Hill of Dreams by Arthur Machen , Fiction, Fantasy

Lucian Taylor is damned - either through contact with an erotically pagan faerie world or through something degenerate in his own nature. He thinks of the damning thing inside him as a faun. He becomes a writer, and when he moves to London he becomes trapped by the increasing reality of the dark imaginings of this creature within him, which become increasingly real. The portrait of a doomed artist - a man not unlike Machen himself.