Somber

--lacking light or brightness and producing a dull, dark, or melancholy atmosphere

Synonyms: black, bleak, blue*, caliginous, cloudy, dark, depressing, depressive, dim, dingy, dire, dismal, dispiriting, doleful, down, drab, dragged, dreary, dull, dusk, dusky, earnest, funereal, gloomy, grave, grim, hurting, joyless, lugubrious, melancholy, mournful, murky, no-nonsense, obscure, sad, sedate, sepulchral, serious, shadowy, shady, sober, solemn, sourpuss, staid, tenebrous,sad

Passage

"They had left the Hogwarts grounds completely; they had obviously traveled mile--perhaps hundreds of miles-- for even the mountains surrounding the castle were gone. They were standing instead in a dark and overgrown graveyard; the black outline of a small church was visible beyond a large yew tree to their right. A hill rose above them to their left. Harry could just make out the outline of a fine old house on the hillside.

Squinting tensely through the darkness, they watched the figure drawing nearer, walking steadily toward them between the graves. Harry couldn't make out a face, but from the way it was walking and holding its arms, he coulld tell that it was carrying something. Whoever it was, he was short, and wearing a hooded cloak pulled up over his head to obscure his face. And-- several paces nearer, the gap between them closing all the time."

Harry Potter and the Goblet of Fire ~J.K. Rowling

Explanation

Overall, the atmosphere portrayed in this passage is extremely gloomy and dark. The descriptive setting compels emotions of sadness instantaneously, which is apparent through the choice of diction that consists of dark or melancholy objects such as: "dark," "graveyard," "black," "old," "graveyard," "hooded cloak," and "obscure," which all exert a depressing connotation. The sense of mystery intensifies the grave situation as well ("Harry couldn't make out the face" and "whoever it was, he was...").