The Reyals are the leaders of the Reyalian Unity (natch). They rule over a diversity of other races by virutue of their vastly superior technology. While not aggressive, they run the show and they know it.
Anytime a new space-faring race is discovered by one of the Unity members, a Reylian ship quickly arrives and offers a choice. Membership in the Unity with all the duties and benefits that entails. Or total exclusion, with swift destruction to any ship which attempts to enter Unity space, ramping up to more severe action for actual aggression.
Physically, the Reyals are not very imposing. Humanoid, they tend to stand close to 2.5 meters, with long thin limbs and elongated humanoid features. Their skin tends to run various shades of blue, and their eyes are red with no noticeable irises.
Socially, not much is known of them, they tend to be brusk and aloof. Outside of first contact they refuse to speak any language other than their own. After inducting a race into the Unity, the new member race is provided with instructional materials (in their own language) to teach Reyalish. This has had the effect of establishing a lingua franca within the Unity.