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. Niflheim spins closest to our world somewhere around Oimelc, the midpoint between the winter solstice and the spring equinox.
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 or bring a lot of heat magic. 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. If the traveler can assume an avian form, it's best to fly over this area; dry land is far between.
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.
Flora:
None at all in the frozen areas, except for cave lichens. There is some scrub on some of the mountain-islands in the watery areas. Supposedly there are some powerfully healing tundra- type plants on the islands, but they are hard to find. Their main powers seem to be that they are adaptogenics - helping the body become stronger and more able to cope with stress.
Fauna:
There are a few arctic-type animals in the snowy regions, and there are seals and other cold-water mammals in the watery region. They can be hunted, although you ought to make sure that you are not hunting on the territory of a hungry frost-thurse. If one does show up while you are standing there with your kill in hand, offering it to them as a gift may get you spared.
Cautions:
One problem that has been reported by travelers to Niflheim is that it is not unusual for frequent visitors to come home with colds, or even pneumonia. Beef up your immune system before you go. Dress warmly, with warmth spells on your clothing and especially your socks. Fire-spells, and the fire-rune Ken, are exceptionally good for this. Be careful, though, because fire spells can make you stand out like a beacon in cold Niflheim. If you want to pass unnoticed by frost-etins, put a camouflage spell over yourself.
Even camouflage spells can't hide actual fires from frost-thurses, though, no matter how small. It is said that if you must bring a captive fire (in a lantern, bowl, or other container) to Niflheim, forget about passing unnoticed, and bring coals from the ever-burning fires of Muspellheim. These do have the power to counteract Niflheim's cold, if only in small ways.
The energy of Niflheim has been likened to a drain, spiraling downwards. There is something about even its still white tundra that suggests constant movement. It is the energy of the compost heap, rotting downwards. It's part of what makes visitors more prone to illness. This world is nearly at the bottom of the tree; only Helheim is lower. Gravity seems heavier here; travelers may find themselves tiring easier, and ought not to take long walks. Flying over Niflheim is possible, but bird-shapers need to take into account the twin problems of sudden, terrible storms and the arrows of sharp-eyed frost-etins.
Bringing a boat with you - especially one that can shrink up and fit in your pocket, magically, is a good way to get around the watery areas of Niflheim. Unless you are a really experienced whitewater rafter, however, surfing the rivers just around Hvergelmir is not recommended.
Residents:
The only permanent residents of Niflheim are the frost-etins and the renegade duergar. As duergar nature is discussed in the Svartalfheim/Nidavellir chapter, we will go on directly to the frost-etins. They are taller than any other giant - twelve to fifteen feet tall in their humanoid form, and more like a thirty-foot screaming, whirling blizzard in their weather-form. In humanoid form, they have pale skin, almost blue for some of them, and hair that ranges from snow-white (and has nothing to do with age) to dark. If they wear clothing, it is usually skins and leather, although some have woven fabric of some sort that they have traded for. In some cases, they may wear the entire skin of a huge animal, like a white bear. This may make it difficult to figure out whether the bear-thing coming for you out of the snow is an actual bear or a bear-clad frost-thurse. Check the aura of any predator before shooting at it; Jotun auras are unmistakable.
As mentioned in the chapter on Jotunfolk in general, frost-thurses are the most territorial and least friendly to strangers of any of the jotunfolk. Fortunately, if you are just passing through, they will usually not bother you. Things that attract their attention: Hunting without permission on their doorsteps. Starting fires close to their homes. Carrying fire, in general. Littering. Invading their caves, thinking that just because it's an empty cave means that it doesn't belong to anyone. If you must use a cave, leave an offering for whoever might own it, perhaps with a note thanking them, or the Gyfu-rune.
There is no one ruler of all the frost-thurses in Niflheim. They are organized into a bunch of loose tribes, and come together for moots and decision-making. Any of the wise elders of any tribe is respected as much as any other. Frost-thurses are keenly aware of the fact that they were the first intelligent beings to be created in the Nine Worlds, and they are proud of that fact. One of their strongest oaths is swearing by Elivagr, the primal frost-river of Niflheim, some of whose nature runs in their veins. In personality, the frost-thurses are private, retiring, suspicious, and somewhat cold. They hunt silently rather than noisily, and they are superb hunters. It is said that they have a certain amount of power over the weather in Niflheim, and can bring down storms, which is another reason not to anger them.
If you run into hostile frost-thurses, one way to get out of being attacked is to tell them that you are looking for the Helvegr, the Road to Helheim, and are lost. They have a great deal of respect for the Land of the Dead that borders their world, and for the Lady who rules it, and they will not molest any pilgrim who is going to that dread land. On the other hand, they are not unaware that some folk lie about such things in order to escape retribution, so they may well call your bluff and insist on escorting the traveler who invokes the Helvegr right to the road, at least within sight of Mordgud's tower. At that point, you have no choice but to walk the Hel-road, so this excuse should only be invoked as a desperate last resort, or if it was actually one of your intended destinations. As harsh as Niflheim is, it is less difficult to extract yourself from than Helheim.
Offerings:
Any food, or small item made of wood (preferably something that is both useful and beautifully made) that will not rot and degrade in the cold. They aren't so much for metal, preferring stone and wood (when they can get the latter). Fruits and vegetables are especially valued, as there isn't much in Niflheim. An elderly frost-thurse once wept with joy when I gave her edible flowers, which was pretty impressive, as I've never seen any of them make such an emotional display before or since.