Star elf

Star elves, or mithral elves or Ruar-tel-quessir as they used to be known, were a race of elves who spent around two thousand years hidden away in the extraplanar redoubt they called Sildëyuir, before trickling back to Faerûn.

Physical characteristics
Star elves looked a lot like moon elves, with light skin and hair of gold, red, or silver. They had violet or gray eyes with occasional gold flecks in them. They were tall for elves, being about 5 1/2 to 6 ft tall, and had a slender build. They liked to wear elaborate tunics but in neutral tones, so as to better remain unseen in the forest. They were strikingly handsome by human standards, even more so than other elves.

Psychology
Aloof and cautious, star elves were unfamiliar with Faerûn and even other races. Isolated in the twilight realm of Sildëyuir, they had no contact with N'Tel'Quess and they liked it that way. It was the war-like and expansionistic humans that caused them to create the realm of Sildëyuir and flee their home in the first place. They generally got along with other elves, though they feared for the moon elves and half-elves of Aglarond who they believed were overly generous and a touch naive.

Perhaps not surprisingly, star elves as a race were generally chaotic in nature rather than lawful. They valued individual accomplishment and rights over the demands of society.

History
In -6950 DR star elves began to gather in the Yuirwood, where a number of green elves already lived. Shortly thereafter the star and green elf nation of Yuireshanyaar was formed in -6600 DR. They had over 5,000 years of peace during that time, largely isolated from the other events occurring across Faerûn. Around -1250 DR the human nation of Unther expanded to the southern coast of Aglarond and battled Yuireshanyaar. The elves lost, and retreated back into the woods. Less than 200 years later the elves were assaulted by orcs during the Orcgate Wars.

In -900 DR the elves begin to notice the rise of Narfell and Raumathar, and knowing that history repeats itself they foresaw disaster in the humans' misuse of magic. With the Untheric humans on their southern coast, orcs in the mountains due east, and two powerful and dangerous human nations to the north, the star elves decide that they needed to find a safer home. The elven high mages created a network of stone circles around the Yuirwood, which was then used to channel a spell that formed the demi-plane realm of Sildëyuir. Finally, in -699 DR the star elves completely abandoned Yuireshanyaar for Sildëyuir. Most of the green elves decided to remain behind.

The star elves of the Yuirwood retreated to this plane and stayed there for a little over two millennia, until they were forced out by alien sorcerers called Nilshais who corrupted their home with strange magic.

Behind the scenes
In the source book Unapproachable East where we have the first illustrations of this race they are drawn with a small light source attached to their heads. This lightsource is never mentioned in the text, not even in the description of the star elves. Since it does not hover, but is attached to a headband they are wearing, one can only assume that it is a common item the star elves wear in their twilight realm of Sildëyuir.