Niflheim

Niflheim is one of the two primal worlds that collided with each other and created the basis for all the other worlds, fire and ice, the beginning of life. This is the realm of mists, and most of it is frozen. Most of the realm, like I have said, is frozen, but because of a great river called Elivagar, a poisonous river with a particularity which is seldom seen in our own world and even the the other world. The river turned everything into crystallized frost. Ancient mountains lie beneath the frozen wastelands, glaciers can be seen all over the place and nothing grows wherever the river and its streams spread.

The myth goes, that when Muspellheim, the fire world, collided with Niflheim, the frost began to melt away in the southern parts of the realm, and from this event the frost giant Ymir was created.
Niflheim, or most of it, to this day is still frozen and very cold, for the river Elivagar still runs in the depths of the icy realm.

Think of Niflheim as an arctic area, where the changing of seasons is seldom noticed by the people who are not used to this kind of weather, unfamiliar with a snow and ice covered world. As nowadays everybody seems to say "Winter is Coming!" because of the Game of Thrones series, well... in Niflheim Winter isn't coming, Winter is always there!
The days are long but the nights are even longer and the skies are rarely clear, so this might give the impression that it is always dark, for those who are able to travel there.

As I have written, more than half of this realm is covered in ice and snow and it doesn't seem to melt, ever. It is a land with thick fogs, blizzards, snow storms, dense mists and occasional thunderstorms. Suffice to say, this is a very dangerous realm, the nature itself will deal with any traveler.

It seems that this realm and its ice melts where it comes near to Svartalfheim, where the terrain is more mountainous. Most of this part is water formed by the melting ice, so much that ancient mountains now look like islands scattered in the water till it reaches Svartalfheim. There are a lot of icebergs floating as you might imagine.

This is the only realm with no structures whatsoever, there are no buildings, exept in the border between Niflheim and Helheim. However, there are inhabitants in this frozen realm, the famous Frost-Etins, living underground in elaborated cave tunnels.

The great well called Hvergelmir lies here in Niflheim and it isn't like the other two sacred wells. Hvergelmir is an enormous hot spring with white waters, with very turbulent waters, from which many rivers flow. This great well is the source of most rivers in the Nine worlds, unlike the regular physics of how a river flows (southwards) these rivers flow upwards, it is natural, we do have some rivers in our own world that do this, flowing through the mountainous terrain and their only escape is due north. However, here in Niflheim, it is uncertain whythe rivers flow upwards, it is an high realm indeed, the very mountains are beneath the snow and ice.
The major rivers that flow from Hvergelmir are so named: Svol, Gunnthra, Fiorm, Fimbulthul, Hrid, Sylg and Ylg, Vid, Leiptr, Sid, Vid, Sekin, Ekin, Gipul, Gopul, Gomul, Geirvimul, Thyn, Vin, Tholl, Boll, Grad, Gunnthrain, Nyt, Not, Nonn, Hronn, Vina, Veg, Svinn, Thiodnuma, Slidr and the great river Gjöll that flows into Helheim.

The watery area of Niflheim is filled with many small islands, like small mountaintops protruding up from the waters. Sometimes they are almost indistinguishable from the icebergs that also float around, sometimes the icebergs collide with them. In this area, as it is closed to Svartalfheim, osome duergar, who have wandered from their native land made their home here and the islands they inhabit actually have the names of the duergar who own them. The most famous is Lyngvi Island, which is claimed by a dwarf named Lyngvi (as it might be expected), in the middle of a small lake called Amsvartnir. This island is used by the Aesir, with Lyngvi's permission, to house the most famous current prisoner in the Nine Worlds, Fenris the Great Wolf, son of Loki. The water on the eastern side of the island is red colored.

Niflheim

Niflheim means, literally, the Home of Mists. It is a cold and partly frozen realm, one of the two primal worlds that collided and created the basis for all the others. In this freezing realm, glaciers and mountains of ice once solidified long ago from an ancient river called Elivagar, meaning Icy Waves. It was a river of poison, of a sort which crystallized all things into frost. When Muspellheim collided with Niflheim, the frost began to melt in the southernmost areas, and the first being, Ymir the frost-giant, was formed. Elivagar's drops are still present in Niflheim, although they are spread throughout the world, but even their diluted form is enough to keep this world cold-to-frozen.

Time and Seasons:

There are seasonal changes in Niflheim, but they are similar to that of an arctic area in this world; in Greenland, the Inuit might easily be able to figure out what season a snow-covered country might be, but it would all look like winter to those unfamiliar with the area. The days are long, several days' length in our time, and the nights are longer, and they extend even further in the winter. Since the skies are rarely clear, it is difficult to tell anyway.

Geography:

More than half of Niflheim is covered in snow and ice that never melts. The weather is often cloudy; it is not named the Land of Mists for nothing. Typical weather might include dense pea-soup-thick fogs that roll over the land, or blizzard conditions, or fog with snow in it (lovely combination for a traveler to get lost in). One might even see thunderstorms with snow. The cold in these areas can be brutal and bitter, and it is best to wear warm clothing. As the Home of Cold, this world does tend to suck the heat out of even stalwart types. It is a very dangerous place to get stuck.

Towards Svartalfheim, the terrain gets more mountainous and the ice melts; here the land is nearly all water with random mountaintops forming steep islands. The waters float with icebergs, so boaters should take care. The water itself is near-freezing cold.

There are no aboveground structures in Niflheim; not that most buildings would survive the dramatic storms anyhow. All the inhabitants burrow underground in caves. The exception is found at the border of Niflheim and Helheim, where Mordgud's Tower stands along the Helvegr. Frost-etins have elaborate cave-tunnels, but wandering into them without invitation, even to get shelter from the weather, is a mistake.

Probably the most important geographical feature in Niflheim is Hvergelmir, the great well called the Roaring Cauldron. Unlike the other two sacred wells, which are small, Hvergelmir is an enormous frothy whitewater hot-spring of roiling, turbulent water from which many rivers flow. It is not safe to be too close to it, as it often overflows its banks and floods the area. Due to the cold, the waters often freeze into ice, and Hvergelmir is surrounded by fantastic naturally-formed ice sculptures like frozen waterfalls. Sometimes one can also see ice sculptures actually created by frost-thurses around the rim; it's one of their favorite art forms.

Hvergelmir is the source of all the rivers in the Nine Worlds, flowing upward through the Tree. Why water flows upward here is uncertain; it is one of the mysteries of Yggdrasil, and reminds one of the old Indo-European idea that fire that fell from the sky and water that bubbled up from the ground was sacred. The major rivers that flow from Hvergelmir are named Svol, Gunnthra, Fiorm, Fimbulthul, Hrid, Sylg and Ylg, Vid, Leiptr, Sid, Vid, Sekin, Ekin, Gipul, Gopul, Gomul, Geirvimul, Thyn, Vin, Tholl, Boll, Grad, Gunnthrain, Nyt, Not, Nonn, Hronn, Vina, Veg, Svinn, Thiodnuma, Slidr (a river flowing with sharp knives of ice and flint whose name means "fearful") and the great river Gjoll, which runs parallel to the Gates of Helheim. As the river Gjoll moves away from Hvergelmir, it goes over an enormous waterfall called Franangr, behind which are a series of refuge-caves that only the brave can reach. One of its claims to fame is that Loki once hid from the Aesir in the form of a salmon beneath Franangr's billows.

Hvergelmir is located close to the gates of Helheim, and next to it emerges the third and lowest extruded root of the World Tree, Yggdrasil. It is hard to envision how enormous this root is. It is the size of a small mountain and runs literally off the boundary of Niflheim and into Helheim; the walls of Hel pass over it like a bump in the landscape. The dragon Nidhogg, a thirty-foot wingless earth-dragon in colors of silver and blue, crawls back and forth over that wall to gnaw at the great root on both sides of the border. Nidhogg can generally be safely observed from a distance; she rarely attacks or even takes notice of travelers.

The watery area of Niflheim is filled with many small islands, like small mountaintops protruding up from the waters. Sometimes they are almost indistinguishable from the icebergs that also float around; sometimes the icebergs collide with them. This area of Niflheim is home to some duergar who have wandered from their native land and dug out the frozen mountain/islands, and their islands actually have the names of the duergar who own them. (There are frost-thurses living on the islands, too, but they don't seem to need to name them.) Courtesy dictates that visitors to the duergar islands find the residents and announce themselves. Some will give you succor, and some will simply grunt and go on their way. As opposed to the family-and- tribe-oriented duergar of Nidavellir, these mostly seem to be antisocial single males, who drifted to Niflheim in order to get more silence and privacy. They don't tend to enjoy visitors, and most prefer to be left alone.

The most famous is Lyngvi Island, which is claimed by a dwarf named Lyngvi, in the middle of a small lake called Amsvartnir due to its dark waters. This island is used by the Aesir, with Lyngvi's permission, to house the most famous current prisoner in the Nine Worlds - Fenris the Great Wolf, son of Loki. The water on the eastern side of the island is stained red; two streams of blood pour forth from Fenris's sword-pinned muzzle and trickle out of the cave mouth and into the small bay. An enormous stone (called Gioll, and covered with protective runes) covers the cave mouth, with just enough room for a person to squeeze through. A hole bored in its center gives forth a magical cord, called Gelgia, woven of the hair of many of the Aesir. It is attached inside to the magical chain that binds Fenris, created sorcerously from the six impossible things. The other end is attached high above to another enspelled stone called Thviti, also covered in runes. The reason that the stones and the cord have names is that they are alive, with guardian wights invoked into them that never sleep.

It is possible to visit Fenris - Lyngvi himself does not think of himself as a jailer and doesn't seem to care one way or the other about the prisoner chained in his basement - but one ought to be strongly aware of one's reasons for doing it. Gawking and mocking at the great beast is not a good enough reason. Fenris may be powerless, but he has relations all over the Nine Worlds who check in on him, and disrespect will get you marked down in a bad way with them. Attempts to free him are futile, as the divine magic that imprisons him is far stronger than even a team of human sorcerers could budge.

Supported by RavenKaldera.