They live on the Plains of Wyndan. I don't know very much about them yet, so bear with me.
What I do know about them is that they breed the best horses to be had in all of Carseld. One of the breeds is a changing horse, so called because they can shift in shape. They can be a plain horse, a unicorn, a pegasus, or a hippocamp. The Raechal are a very warlike people, they are very adept at fighting from horseback and use lances, spears, bows and swords. The best of the warriors have a mental bond with their horses similar to that of the dragons with their Riders.
As much as I hate to say it, they are similar to the Anglo-Saxons in the way they live. They love their freedom, and if imprisoned will often go mad. (this may be a result of their living on the wide open plains, where the wind blows freely over leagues of nothing but wild grass and horses . . . okay enough poeticness. )
They have a predominance of black hair. Eyes are all colors, but primarily blue or green. The skin does not tan, but instead whitens with age and exposure to the sun. Thus, the older Raechal will have striking black hair and very pale skin. The infants are relatively dark.
They have a mixed diet, using very little spice or salt. The meat is composed of the deer-like creatures that live on the plain with the horses, and fish that they catch in the nearby ocean, since they are on the coast. They do mostly shallow fishing, and do not like deep water, thus want nothing to do with boats or ships.

That's what I have about them so far. If it sounds disjointed, you need to know that I was making this up as I went along. Please tell me if you have any objections, questions, suggestions, etc.

Lady Eruwaedhiel

How does their skin get lighter? Does it have a different type of pigment? Or is it magic? They sound interesting, the shapechanging horses sound pretty cool too!

I think they sound very interesting! They almost sound like a combination between American Indians and Anglo-Saxons.
I think it's neat that the older ones have contrasting skin and hair, and that the Raechel breed shape-changing horses!

I'm not sure you would be able to tell the difference unless you looked very closely. I believe their ears are set higher on the head than humans. Other than that, I'm not sure.

Here is a little more I have about them:
They are fond of ale, mead, etc. They love parties and are generally very cheerful and quick to laugh, however their temper is also very close to the surface.

Their political system consists of a queen in the capital city and individual rulers in the smaller towns. Once a year there is a gathering of these to discuss whatever (I'm rather vague on most of my politics--it's one of the few things I hate to write.)

They have an atheistic religion, having been deceived early in the history of the world. They are however fairly easily converted when shown evidence--they aren't particularly steadfast in anything.

The young people are given heavy responsibility fairly early. The young women are not only encouraged to learn how to maintain a home, but to fight and ride as well--thus there are almost as many female warriors as male on the field of battle in the occasional skirmishes. Many of them choose not to marry but instead carry on the tradition of breeding and training horses. Those who do marry predominantly bear twins and triplets. Single children are rare, and large families abound.

And, as before, I'm just making most of this up.