。
It was a moonless night of darkness.
Literal
Moon [even-も] not-rising darkness-night was.
A short atmospheric opener. 闇夜 ('dark night,' 'a night of darkness') is a compound: 闇 (darkness) + 夜 (night), used in narrative and literary contexts for nights without moon or stars. 月も出ていない ('the moon isn't out either') is a relative clause modifying 闇夜 — the も here is emphatic/inclusive, 'not even the moon,' emphasizing the totality of darkness. Note that 出ている ('be out') for the moon is the resultative/state use of ~ている: 'in a state of being out.' A perfect set-up sentence for a suspense or horror scene.