The Nereid (also called Water-Sprites by the Redguards) are mer-like, feminine water spirits that live near bodies of water and can often be heard singing an angelic, but transfixing melody. They are known practitioners of water magic, an obscure form of magic, and can either become hostile or tolerant of people's company. Generally speaking, the Nereid are an intelligent-folk that more often than not, protect the land they live on and its denizens, even claiming old ruins as their own haven.
Netch (or netches) are large and generally peaceful creatures native to Morrowind that resemble airborne jellyfish with the size and disposition of cattle, floating through the air supported by internal sacks of magical gases. The barbs on a netch's tentacles contain active nematocysts, making them deadly if provoked. Adolescent netches are called calves or netchlings and resemble female ("betty") netches. Male ("bull") netches are larger than female ("betty") netches; the latter can be provoked into aggression more easily. They are usually peaceful but can be defensive of their territory, particularly during breeding season. When betty netches and calves feel threatened, they secrete pheromone oils that drive bull netches mad, turning them aggressive.
The Nightmare Courser is a Daedra that takes the form of a black, flame-wreathed horse. Many conflicting legends surround its mysterious origins, although it is associated with Mehrunes Dagon. It is sometimes used by mortals as a mount, although its chaotic temperament makes this a difficult task. Although superficially similar in appearance, the Courser bears no relation to the Hell Hound.
Nix-hounds are medium-sized bloodsucking insectoid predators that are native to Morrowind, as well as having migrated to Solstheim by the Fourth Era as a result of the Red Year. Its cousin, the rogue nix-hound, is larger and much more dangerous.
When young nix-hounds emerge from their chrysalis, they can immediately drain up to four similar sized prey a day using their proboscis. They have been noted as being very opportunistic whilst searching for food, easily killing small animals and children even whilst at this early development stage. Adult wild nix-hounds are aggressive pack-hunters, with many men and mer meeting their end from an unsuspected ambush. Nix-hounds sustain themselves by draining prey of bodily fluids, leaving behind a 'meat-husk' that other creatures such as alits will eat. Common prey include baby guars, goats, kwama pupae and ash hoppers.
Numidium (or Anumidium), also known as the Brass God, the Prime Gestalt, the Brass Tower, Walk-Brass, and Big Walker, was a colossal construct of Dwemer origin. It was constructed by Dwemeri Tonal Architect Lord Kagrenac to be a new god, powered by the Heart of Lorkhan, made to retake Resdayn from the Chimer and make the Dwemer race immortal. The Dwemer vanished from Tamriel before the Brass God could be activated, though their disappearance may be directly related to this endeavor.
The Numidium was, in practice, a weapon of devastating power. A "thousand foot tall automaton, a golem or an atronach[nb 1] of sorts", it was used by Emperor Tiber Septim to complete his conquest of Tamriel at the end of the Second Era, but was destroyed afterward. The golem was rebuilt and reactivated centuries later, and became the center of the phenomenon known as the Warp in the West, after which it was destroyed again. Temporal distortions have accompanied each known use of the Numidium, to the point that the Warp in the West is sometimes known as the "Second Numidian Effect".
A second Numidium, Akulakhan, was partially constructed in Morrowind in the late Third Era by Dagoth Ur. However, the destruction of Kagrenac's enchantments on the Heart of Lorkhan in 3E 427 prevented its activation.
A beautiful creature, but not without its danger. Nymphs require silver or better weapons to be harmed, have some inherent magical abilities, and drain their opponents' fatigue in addition to health. Nymphs have their own melodious tongue, which sounds similar to Ayleidoon and faerie but shares none of the vocabulary.