It's usually not a great idea to judge a whole race before you meet them, but in the case of the Uranusians, it's usually okay to make an exception. To a man, they are pessimistic and completely foul to be around. It's not that they curse or make fun of people... They aren't violent or remarkably left-wing... It's just that they are drab and boring. Some are doomsayers, too. No matter what you do, it'll eventually end in death.
And come on. No one likes to hear THAT.
They have a distinct lack of endorphins to their brain... The exact opposite of the Mercurians, in fact. They like the dark, and some of them actually see quite well in it... Their underground tunnels are very dim. Some Uranusians have never even left the underground, claiming it's not worth it, and it's just another way for death to catch up with them faster.
Umbriel is just as bland and boring. The cities don't have names... It takes far too much effort to come up with one. Instead, they are catalogued by number... The second largest and the most populated city has a designation of 008. All cities are underground about a mile, and are a series of tunnels supported by planetary pillars in-between. Hauses are as boxy and boring as possible. Uranusians really care nothing for beauty. It just needs to function as a house, and that's it.
It's not that Uranusians care about nothing... They value family life and friendships... Anyone that can listen to them complain and doomsay for hours on end and provide the same is considered a close friend and a confidant. Family and friends are important in life... Things that aren't... material posessions, etc... well, they don't really seem to matter to most.
The one power all Uranusians share is the ability to absorb, manipulate, and project electricity. Their home planet around Rigel was charged with electrons and energy fields, thus, the Uranusians evolved a very unique defense against being electrocuted. As they are walking generators, there aren't any power systems on Umbriel. If they want something to work, they just zap it.
There are always some that don't fit the norm, though. Those Uranusians that aren't completely absorbed in their race's negativity usually head offworld. Some of them are actually pleasant company... Those that aren't usually mellow with time. Likely, their attitude is not only a product of their body chemistry, but a combination of that and their bland homeland as well. Once out in the world, they fit in just like anyone else.
Uranusians make excellent philosophers, mathematicians, and fit in to a lot of other academically geared fields. Due to their mental determination, they also make surprisingly good athletes. Some like to participate in Earth sports such as soccer and baseball. No one knows of any Uranusian sports, though there are rumors that one may be in development.