Night

Although not actively worshipped universally, Night is acknowledged as ruler of the dead, lord of darkness and evil, and creator of the Volgs and other monstrous creatures of the world by just about every religion. Small details vary from religion to religion, but all religions agree that Night is one of the four divine entities that rule over the cosmos. However, Night is outcast from, and opposes the other three.
The Universal Church sees Night as a male divinity. It accepts Night as a necessary part of creation, if an undesirable one. As such, most churches contain a small area within the main worship area devoid of any decoration apart from a single plaque reading, "Lest we forget the Night," or something similar. Although the Church acknowledges Night, it also professes that Night's servants, such as Volgs and Darkers (see below) must be fought.
The Isyar see Night (as with all the gods) as a genderless being, who originally worked with the other three gods to overthrow the Old Gods. It was only when the majority of the Old Gods' power went to Cosmos (called All-Father by the Universal Church) that Night split from the others out of jealousy. Since then, Night has worked to oppose the other gods in all ways. In addition to the standard domains of darkness, death, evil, and Volgs, the Isyar also see Night as the patron of Isyar born without magical power or the ability to fly. They also see the slow diminishing of the Isyar people as a result of Night's direct manipulations.
Officially, the Ninifins refer to her as Nyx, but they rarely utter that name, preferring instead to refer to her as the Dark Lady. They do not see Nyx as a full-fledged god, but rather a demon. Otherwise, they view the Dark Lady in much the same way as other religions, except they also believe she created the Isyar as her servants, despite the fact other human ethnicities generally think of Isyar as angelic beings. They believe Volgs (the usual evil creatures in other human religions) are just stories made up by the Isyar to hide the Isyar's own evil natures.
To the Delams of Singea, Night is a genderfluid being, sometimes male, sometimes female, sometimes neither, who tempts people off the path of enlightenment and blocks reincarnation.
Little is known of specific Volg religious practices, but it is well known that, as creations of Night, they all worship him exclusively, and reject all other gods. (Of course, while this is "well known", there is very little documented evidence to actually support this.)

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Darkness Worshippers

While not sanctioned by any of the main religions, there are people who actively worship Night. Known as Darkness Worshippers, or more commonly just Darkers, these people tend to keep their devotion secret from anyone who is not also a Darkness Worshipper. They call themselves Servants of Sunset or Servants for short and consider the term "Darker" to be a slur. The Servants use a goat's skull as the symbol of their allegiance, and all Servants bear a tattoo of a goat skull (in various designs) somewhere on their body, usually somewhere hidden from casual observation.

- typical symbol used by Darkness Worshippers
(illustration from an open source image coloured in GIMP)

Divine Classification

God

Church/Cult

Servants of Sunset

Appearance

Varies depending on the religion and/or ethnic group, but usually human-like (of varying gender), often shrouded in shadow, and often with pitch-black eyes. Isyar generally depict Night as an Isyar with withered, almost skeletal wings.