Svartalf

Svartalf or Svartalves or Svartalfheim are smiths from the Nevernever. First mentioned in Dead Beat (Ref?) and again in Proven Guilty and Changes, and they are first seen in Cold Days. They also appear in several short stories, like "B is for Bigfoot".

Description
Svartalves are peerless artisans of the supernatural world. They are very private and independent and they "tolerate absolutely no nonsense". They are not very generous. "No one wants to get on the bad side of a Svartalf." They are very fond of beautiful things and creatures, including humans and other humanoids. In Leah's words "A svartalf lusts after beauty like a dragon does for gold." They look like grey little aliens, although the females are a bit more human looking, with attractive features and long silver hair, but they can and do wear a flesh human disguise much the same way the Red Court Vampires did.

Their craft wares are sold out of a shop in Norway. They are very powerful and skilled in the Magical Art. (ref?)

Svartalves can be prickly about their territory. The Svartalves take their honor very seriously and are very old school; they are known to react very badly to anyone violating guest right. (ref?)

Svartalves seem to take sex as payment for certain favors, or compensation for certain transgressions, as long as the person offering it is up to their standards of beauty. Such as when Thomas is captured spying he makes a deal to stay until the morning with the female Svartalves in order to be set free. Leah tells Molly that the Nordic Myth about Freya's stolen necklace is translated in a very prudish manner. In the myth, Loki pawns the necklace to the Svaralves, but they agree to return it if Freya will kiss each and every one of them. In Leah's words "They did not relinquish one of the most prized jewels in the universe for a society wide trip to first base."

Dead Beat
In Dead Beat,

Proven Guilty
In Proven Guilty, Harry used a pair of hawk-wing feathers made of gold by Svartalves to anchor Air in a Ritual to test out Little Chicago.

Changes
In Changes, the summoning ring in Harry Dresden's Lab has been upgraded to a five foot hoop of braided copper, silver, and iron. It cost Harry three grand from a svartalf silversmith. The materials aren't all that expensive but the svartalf needed to be compensated to work with iron. "Each metal strand in the braid was inscribed with sigils and runes in formulae that harnessed and controlled magical energies to a far greater degree than any simple circle. Each strand had its own string of symbols were so tiny and precise that only a svartaf or maybe an Intel could have pulled it off. Flickers of light slithered around each strand of metal, red light, blue and green dancing and intertwining in continuous spirals."

Cold Days
In Cold Days, Molly Carpenter's apartment was built for her by Svartalves. She said she bought it with honor. Harry thought they wouldn’t be happy if he dragged a personal fight with Fix at Molly’s apartment should Fix come looking for him there. Murphy said that Molly’s place is "under aegis of “Svaralfheim” no one gets in without major assault." Molly has to go with Thomas each and every time he leaves or return to her apartment or they won't let him back in.

External references

 * Svartálfar - Wikipedia
 * Svartálfar - Wiktionary