Interestingly, the Rattataki resemble humans in nearly every way save for skin color and lack of hair, but there is actually a canon reason behind these differences. Supposedly, during the galaxy's youth, many humans from the Core worlds ventured out into unknown space only to be stranded and forgotten. For instance, had Gav and Jori Daragon not found the Sith Empire, they would have probably become victims of their own space exploration. However, unlike the Daragons, the Rattataki ancestors presumably landed on Rattatak, a harsh, uninhabited world in the far Outer Rim, never to be heard from again -- that is, until the Sith Empire rediscovered them.
The surface of Rattatak was nearly impossible to live on. Most of the living creatures lived underground. After centuries of little light, presumably, the Rattataki eventually stopped growing hair, and their skin became multiple shades of pale grey.
Fanon creators and roleplayers believe that the dark markings on a Rattataki's face are tribal and extend to the rest of the body. However, there is no canon to substantiate or discredit that claim. Personally, I like to think they are similar in origin to the Zabrak tattoos (jato): tribal markings associated with a rite of passage. But there's nothing in canon to back that up.
As is common in the Star Wars universe, the first instance of the Rattataki culture in canon represents the quintessential part of the whole species. In this case, I'm talking about Darth Tyrannus demanding that Asajj Ventress display her prowess in the gladiator pits on Rattatak.
According to canon, Rattatak does not produce enough resources for its inhabitants, and since the planet sits on the edge of known space, the essentials of life are rare. This led to an extremely violent society of warring tribes. Even much of the judicial system uses violent competition to determine the guilt or innocence of an accused. In a parallel to some our own Earthly history, many of the criminals of Rattatak would be thrown into the gladiator arena to battle there for the remainder of their lives.
If we take Asajj Ventress as an example (though she was later determined to be a Dathomiri posing a Rattataki), we can see that generally the male and female Rattataki were given fairly equal weight in society, so much so that it was not uncommon for men and women to battle each other in arenas.
Like the humans they supposedly descended from, the Rattataki are commonly Force sensitive. However, the Rattataki culture does not have its own Force practices.
As I noted earlier, Asajj Ventress was the character that introduced the Rattataki species to Star Wars canon, but she wasn't truly Rattataki herself, compounding confusion about the species. In fact, she was a Dathomiri. Still, her backstory set up much of what we know of the Rattataki's connection to the Force and the species' place in galactic history. If you are interested in the Rattataki culture, you can use Ventress as an example because things only start to fall apart when she was introduced as a Nightsister.
Rattataki, interestingly, are the only playable species with an introduction to the greater universe stemming from events during the Imperial invasion. During its occupation of the galaxy, the Empire stumbled on Rattatak. (How you stumble on a planet on the other side of the galaxy from your primary invasion force I'll never know... but there it is.)
A young Darth by the name of Vich loved the Rattataki warrior culture and the gladiator arenas. The Empire practices what is commonly known as High Human Culture, but Vich put that aside and began to create his own army of Rattataki soldiers and Force-trained Rattataki acolytes to overthrow the Imperial leadership. Of course, this little coup did not work, and most of the Rattataki following Vich were executed. However, there is a rumor that some were simply enslaved and integrated into Imperial society.
Tell me about your Rattataki in the comments. Did you use some of this history to form your character? Are you going to use it now? Has this direct connection inspired you to create a Rattataki alt? I look forward to reading your thoughts.
The Hyperspace Beacon by Larry Everett is your weekly guide to the vast galaxy of Star Wars: The Old Republic, currently in production by BioWare. If you have comments or suggestions for the column, send a transmission to firstname.lastname@example.org. Now strap yourself in, kid -- we gotta make the jump to hyperspace!