Joshua ice is a combination of water and air some people say that nidhogg used to be of ice affiliation and to answer the other question with enough practice you can summon and learn from a dragon but be respectfal as they are very intelligent on par with or surpassing humans
The reason that Nidhoggr is associated with ice is because of the realm he lives in: Niflheimr. That being said, Heathens do not recognize any set of "elements" because we make no claims that there are certain energies that make up all of the energies of existence (except the Periodic Table of Elements, of course). Instead, we honor ice and other forms of energy as forces of nature. While you may not consider "ice as an element", we do incorporate ice into our practices, depending on who we work with (frost thurses are directly made of and/or associated with ice, for example. Like Nidhoggr, there are plenty of beings who live in realms made of ice or associated with it).
I would not suggest using Fafnir or Nidhoggr in your path unless you understand who they are, what they are, what they're associated with, and what their personalities are like. Most people wouldn't actually get along with either because they're not "friendly" like a nurturing spirit or deity is. I'm personally not a fan of just mixing pantheons without respect and regard of what and where they came from. To do so without research into the original cultures is insulting on many levels.
I don't think it's from Conway, but I can check. I have read it on a few sites, plus other practitions I have spoken to have called on them by those names [the four elementals, not Nidhogg] I was a little confused when I saw Fafnir was the Dragon of fire as he's from Norse mythology, but I guess the names and dragons come from all corners. Most call the earth Gaia. I have met with the dragons in the astral, but they don't speak to me like others, don't know why, so I can't tell you what they've said, when I first addressed them by name each nodded, that's all I can tell you as a 'confirmation'. Take it as you will.
Niflhogg is accociated woth earth. Also Niflhogg doesn't live in any realm. Niflhogg if you look at that link, circles the world tree and gnaws at the roots. The roots connect to all the nine realms so Niflhogg doesn't live in any realm. Also Niflhogg is a earth dragon.
Like with ice dragons however, it's not seen as the main five. Grael, Sairys, Fafnir, and Naelyon are seen as the four ruling dragons of the elements and the final being [by most] Chaos Dragons who do not have a ruler. Chaos is believed to be the fifth element because how unpredictable they and life can be. Spirit Dragons can be called on, but I know some practitioners who view them as the spirits of dead dragons and not an elemental Dragon. Ice dragons fall under Naelyons rule as a subclass of water. But I guess if you wish to work with an ice Dragon go for it, I have trouble with Fanir so I try to limit my contact with him.
After looking into it a bit more, I see that this is from DJ Conway's book called "Dancing with Dragons". Again, DJ Conway is known for taking Norse concepts, not providing the background to them, and taking them out of context to work into her ideas of her practice. I don't think it's right to do so. And DJ Conway tends to be wrong about a lot of the stuff she takes from.
Josh, Nidhogg is a Rokkr deity- but also considered to be dragon/serpentine. Much like how Fenrir is a Rokkr deity- but also a wolf. Nidhogg is said to be at the roots of Yggdrasil, near the shore of Nastrond (the Corpse Shore) which is located near Niflheim (where the ice is) so I'm assuming that's as close to associated with ice as it gets. However, I would say that Nidhogg is more of an earthy deity, as Nidhoggr is the embodiment of decay (known as Corpse Eater because he eats corpses and recycles them). This is why I have an issue with him being included. He's not a deity known to work with anyone.
Fafnir is another one that just doesn't make any sense to me. Interestingly, the only association I've found between Fafnir and fire is the fact that the Marvel universe portrays him as a fire breathing dragon. Nowhere in the original myth does Fafnir have anything to do with fire. Nor is Fafnir originally a dragon: story goes that Fafnir was a son of a rich dwarf. Long story short, due to a conflict with Odin and Loki- Loki gives the dwarves a cursed ring. The cursed ring turns Fafnir into a jealous murderer and he kills his father and takes his gold. The ring causes him to become greedy and he turns into a dragon. He is then killed by Sigurd, the Hero
. DJ Conway's description on him goes: "The Element of Fire governs the Southern quarter of the circle. It's Dragon Ruler is Fafnir (faf'near) who oversees the Dragons of Fire. It's color is pure red; it is considered warm & dry. The positive associations of Fire are; Noon, Summer, the Dagger & the Sword, Candles, Incense Burner, the Sun, Blood, Enthusiasm, Activity, Change, Passion, Courage, Daring, Will Power, Leadership. Negative are; Hate, Jealousy, Fear, Anger, War, Ego" . She's just taken the dragon image and name of Fafnir from Norse tradition, and plugged it into what she wanted to do with it- as she's done before. If anything, Fafnir was said to breathe poison onto the land, wilting the nature. Not fire. There's not a single thing linking him to fire.
These two just seem to be taken from Norse tradition with little understanding of their background, which is why it seems to odd to me. I've yet to find a single link (not a link that's from angelfire, or other unreliable sites) that talks about either of these in a different aspect.
Personified has a deep understanding of these figures. They are part of her native heritage and her practiced faith. Their origin has nothing to do with Dragon magic and the elements as you are discussing it. They have only been smashed into the concept of dragon magic, much like many other such entities where dragon magic is discussed at all.
Perhaps you should consider that you are the one that lacks an understanding of these entities. Personified has explained to you that they have nothing to do with dragon magic and such practices. You are referring to sites that basically restate the same concepts that are more imagination that historical tradition.
