'Gloom' in the Bible

‘Thus says the Lord God, “On the day when Assyria went down to Sheol (the place of the dead) I caused mourning; I closed the deep [subterranean waters] over it and restrained its rivers. And the many waters [that contributed to its prosperity] were held back; and I made [the heart of] Lebanon mourn for it, and all the trees of the field wilted away because of it.

Just as a shepherd looks after his flock during the day time while he is with them, so also I'm going to watch over my sheep, delivering them from every place where they've been scattered during the times of gloom and doom.