Dusk Elves

The Dusk Elves are a group of elves who live alongside the Vistani by Vallaki. None of our heroes had ever heard of "dusk elves" prior to their time in Barovia, though whether this is because all the remaining dusk elves are here, or because in the intervening years since Barovia was separated from Faerûn those elves have integrated into other communities, or simply live in seclusion wherever they are, is unknown. From Ayduin's observations, there are several similarities between dusk elf aesthetics and customs and those of wood elves.
Most of the information our party has on the dusk elves has come from Rudolph. When Sylvain asked him about the group, after an initial bit of hesitation, he gushed the whole story, though he admitted it had been a while since he'd heard it, so he wasn't certain he had all the details right. However, Rudolph says the dusk elves have been in Barovia for centuries, and that long ago, they killed one of their own — a female dusk elf of whom Strahd was fond. In retaliation, he killed all the female dusk elves, including female children, condemning the dusk elves to slow genocide. As such, all the dusk elves at the Vistani camp have been alive for at least a few centuries, and were all alive for whatever incident led to this act.
Upon speaking to Kasimir, the leader of the dusk elves, our heroes learned that the woman in question was his own sister. Unlike Ireena, his sister willingly sought Strahd out, craving power and immortality. Their fellow dusk elves killed her, Kasimir said, because they feared what she might become if they let her pursue Strahd.
In remorse and grief, the dusk elves clipped off the pointed tips of their ears, as a mark of shame for what they had become. They seem to largely keep to themselves at the camp, though they're apparently excellent trackers — Rudolph says they're pretty depressing to be around, a real bummer of a group. To be fair to the dusk elves, Kasimir smiled a lot while our heroes talked to them, even if he was mostly doing that to hide the fact that he was speaking treason in Elvish, and Celegal seemed downright friendly!
According to some history books, the dusk elves were, along with the coill cailleacha and the Vistani, the original inhabitants of the valley now known as Barovia.

Known Dusk Elves

Celegal

Celegal, according to Rudolph, was the group's finest weaponsmith, known for the quality of his bows, crossbows, and accompanying ammunition. This apparently extended to doing business with Vallaki, making him one of the only people at that Vistani camp known to have regular interactions with the nearby town.
He specialized in wooden carving, doing very little metalwork aside from the most basic shaving of pre-forged metal bolt tips and arrowheads to improve their aerodynamic qualities. Most of his bows and crossbows featured elaborate wooden carvings of animals, nature, elven words, and runes, and other symbols. To those better able to pick out the nuances of elven age, he looked as though he was likely quite young when Strahd struck down his people.
Celegal was killed while disarming traps set by Dr. Rudolph van Richten.

Feodor

Feodor was, according to Kasimir, one of the most skilled dusk elves when it came to the treatment of pelts and furs. Kasimir said he'd give word to Feodor to come find Bodaway to discuss what might be done with the dire wolf pelts our heroes acquired while waiting for a cultist to wake up.
Feodor was killed while disarming traps set by Dr. Rudolph van Richten.

Kasimir

Kasimir, according to Rudolph, was the leader of the dusk elves. Though he had no formal power at the Vistani camp, Rudolph suggested saying hello and paying their respects may benefit our heroes in the long run, if they thought they might be in Barovia for a while.
Upon visiting Kasimir, our heroes learned he may be a helpful ally indeed — though he couldn't answer all their questions, he seemed much more knowledgeable than most of the people they'd spoken to. Makes sense, seeing as he's exponentially older than most of those people. He seemed eager to help our heroes strike back at Strahd, and told Sylvain and Ayduin that he knows where to find the golden knights guarding a white tower, and that nearby is a temple full of forbidden knowledge which he believes may hold the key to defeating Strahd. However, he knows the journey is very dangerous. He said if and when they decided they were ready for a challenge, he would go with them. He has at least some magical ability, based on his offer to enchant Ayduin's bow.
Following our heroes' departure from the Vallaki Vistani camp and Bodaway's message from the Raven Queen for him, Kasimir was escorted by Arrigal Yezhov and unknown parties to Castle Ravenloft. Recently, he was set free by none other than Ismark Kolyanovich, and is now travelling along with most of our heroes on the Ethereal Plane, seeking to undo Strahd's rule once and for all. It is obvious, however, that his months of imprisonment in the water-logged dungeons have taken a toll.

Ruslan

Very much the strong, silent type, this dusk elf was accompanying Arrigal on his search for Arabelle when our heroes came upon the pair. Ayduin later learned this elf's name is Ruslan, and rapidly figured out that Arrigal is carrying a torch for him. Sylvain also figured this out over the course of five seconds of Arrigal talking about him, on their return to the camp. It seems that Ruslan has some fondness for Arrigal, too, as he'd grown concerned and gone looking for Arrigal when he was gone longer than expected after going after the party. Ultimately, Arrigal sought Ruslan out in turn, and found him half-dead of infected wounds from needle blights, hiding in the wine cellar of Argynvostholt. When the party returned, Arrigal had only recently brought Ruslan back, and Ri-An cured him of the infection that was threatening his life. According to Arrigal, he is "good," so take that for however much you think Arrigal's word is worth.

Unknown Dusk Elf I (Guard)

This dusk elf was guarding Kasimir's home when our heroes went to see him.

Unknown Dusk Elf II (Guard)

This dusk elf was guarding the cabin where Ruslan was recuperating when our parties went to the Vistani camp a second time. He thinks Arrigal is a nuisance, and Ri-An broke his foot.

Unknown Dusk Elf III (Healer)

This dusk elf was the one tending to Ruslan's wounds when our heroes assisted in his recuperation. By the looks of the materials around him, he is not a magical healer like a cleric or a druid, but one who relies on knowledge of medicine and herbal compounds. He seemed grateful for Ri-An's assistance.
Unknown Dusk Elf IV (Basket-Carrier) This dusk elf was seen hurrying from the cabin where Ruslan was recuperating from his wounds, bearing a basket full of bloody, pus-stained bandages.