There are many reasons he wrote dark and chilling stories and poems. The main reasons though, he had a very rough upbringing and he was mentally ill and on several drugs as well as being an alcoholic. But, if you see things like I do, you find the sheer beauty in the little picture of the big image that's gruesome.
dark and gloomy
Depressing
The chambers of the castle were dark and gloomy. Just because our team lost, there is no need to be gloomy and dejected.
This rainy weather has made everything so dark, depressing and gloomy.
bleak
gloomy, dark
Stygian is a Dark, Gloomy place
Stygian.
dark and gloomy
dim, shadowy, cloudy, dark
gloomy, dark, dull, bleak
lowering