'Dark' in the Bible

To understand a proverb, and the interpretation; the words of the wise, and their dark sayings.

who leave the upright paths to walk on the dark ways,

The way of sinners is dark; they see not the cause of their fall.

In the twilight, in the evening, in the black and dark night:

Who says, Oh! who says, Ah! who has violent arguments, who has grief, who has wounds without cause, whose eyes are dark?