Terry Pratchett sums up the Elves of Midrea

Elves are wonderful. They provoke wonder.
Elves are marvelous. They cause marvels.
Elves are fantastic. They create fantasies.
Elves are glamorous. They project glamour.
Elves are enchanting. They weave enchantment.
Elves are terrific. They beget terror.
The thing about words is that meanings can twist just like a snake, and if you want to find snakes look behind words that have changed their meaning.
No one ever said elves are nice.
Elves are bad.
Terry Pratchett, Lords And Ladies

The Elves of Midrea hail from a parallel dimension, the Violet Realm called Faerie. Its an tremendously magical place where pretty much everyone and everything there is magical in some form or another. The Elves themselves are closely related to humanity, having a similar appearance and enough in common with humans to bear fertile offspring about 1 time in 10.

The resemblance however stops there however. While Elves seem like humans they are mostly borderline sociopaths driven by capricious whims. They may have functional immortality but the years weigh on them and can induce a sort of madness as over time . They are all as was once said, Mad, Bad and Dangerous to Know. The older the Elf the worse they worse they are . As their magic power increases (its accumulative in everything the eat and drink) they can become weirder and more inhuman. All Elves are chaotic.

Do to the magic that courses through their bodies Elves are immune to aging and normal diseases, have great resistance to various sorts of undead taint and possess superior senses including night vision. The also do not scar and given time can even regenerate lost limbs.

Elves cannot lie or break promises but they can twist words and are good at it. The Ley of Halet is a popular folk song about a legal debate between a Grey Elf and a Vara Truth Speaker . There are about 10 or 12 known versions, making the origin suspect but in all cases the Vara seems to be the winner which tell you something about Vara legalism.

There are three main "groups" of Elves

1st are the Dark Elves, who live underground and are rumored to worship the ancient Gods of Midrea including the Flame and the Spider. No Dark Elf is decent and they do not use scimitars just in case anyone asks. Dark elves are always Chaotic Evil.

2nd are the Grey Elves. These live in the Elaven Wood, a titanic forested area and the home of the Violet Gate. These Elves are more subject to whim then most but unlike the Dark Elves do not hate humanity. Unlike humans and some other Elves they cannot have a connection to the Divine and cannot use Divine Magic .They are always Chaotic Neutral.

3rd a White Elves. These Elves live in Aradia and while given to caprice like other Elves seem to have a moral center of some sort. They are connected to the land in ways that other elves are not and can use natural magic as well. They are not wise to be around for most people but Aradians are Elfwise and seem to be able to coexist with them. They are always Chaotic Good and make suitable PC's.