In the following passage from Book 1, Chapter 7, Hardy establishes the motif of darkness, which becomes a regular occurrence in The Return of the Native. The narrator employs dark visual imagery and several metaphors and similes referencing darkness to underscore Eustacia Vye's inner turmoil:

Egdon was her Hades, and since coming there she had imbibed much of what was dark in its tone, though inwardly and eternally unreconciled thereto. Her appearance accorded well with this smouldering rebelliousness, and the shady splendour of her beauty was the real surface of the sad and stifled warmth within her.

In this passage, Hardy utilizes the metaphor of Hades—the underworld in Greek mythology—to depict Egdon Heath as a hellish place for Eustacia. The dark imagery used to describe Egdon Heath reflects its effect on Eustacia, as she is "stifled" and "shady" within it. The dark "tone" of the place, which she has "imbibed," refers to the drama, secrets, and danger associated with the heath. The "shady splendour" of Eustacia's beauty likens her visually to the moorland, which is both beautiful and frightening in its darkness.

The motif of darkness also appears in Book 1, Chapter 8. Hardy's narrator further explores the link between darkness and the moor's menacing aspects as Johnny Nunsuch walks home alone at night:

The thorn-bushes which arose in his path from time to time were less satisfactory, for they whistled gloomily, and had a ghastly habit after dark of putting on the shapes of jumping madmen, sprawling giants, and hideous cripples.

In this passage, the tactile and auditory imagery of the heath being filled with "thorn-bushes" and "whistling gloomily" serves to illustrate its eerie, perilous nature. Darkness is linked to the theme of mixed communications and deception in this novel: things not being as they seem in the night is a physical manifestation of this. This sensory language of darkness emanating from the heath itself is also consistent with its effect on Eustacia. There's a sense that the heath is a bad influence on some of those who live on it, "darkening" their lives.

Finally, in Book 4, Chapter 1, Hardy extends the motif of darkness to the cycles of natural life on the moor. He uses a simile to liken the cycles of the year on Egdon Heath to the periods within a day:

It was the one season of the year, and the one weather of the season, in which the heath was gorgeous. This flowering period represented the second or noontide division in the cycle of those superficial changes which alone were possible here; it followed the green or young-fern period, representing the morn, and preceded the brown period, when the heath-bells and ferns would wear the russet tinges of evening; to be in turn displaced by the dark hue of the winter period, representing night.

Here, the "dark hue" of winter refers to both the "dark" season of the year and the darkening of each evening. Hardy describes the natural cycles of life on the moor through visual imagery of blooming and rotting. This makes the moor seem as if it is the central, controlling aspect of life for Hardy's characters, both their clock and their calendar. The moor's darkness is never far away. Even in the "flowering period" of summer, any move away from darkness is "superficial" and temporary.