All of these are available via DriveThruRPG and Far Future Enterprises.
PDF. 44 pages, color cover, black and white interior art.
While not the first Traveller alien I encountered, this is the first module or data file for the various aliens Traveller has to offer. This one seemed like a no-brainer to me at the time. I had read Joan D. Vinge's "psion" earlier that year and between the Caitian and Kzinti (introduced to me by Star Trek) I was primed to want a Cat-like race in space.
The book covers the basics. Aslan physiognomy, which includes some evolutionary details and how it plays into their current civilization. Their political structure (or almost lack thereof) is also discussed. While the Aslan (named such by the first human explorers to make first contact) are described as proud warrior race, they are not really a unified one.
We are given a bit of their history and their forays into space and their encounters with the Imperium. We get a bit on their psychology, which includes the territorial nature of the males (explained the loose confederacy) and their ritual duels.
The next large section is Aslan character creation. This covers the basic character creation going back to the 3 LBBs and "Expanded" character creation for other types of characters.
We are also given background on the Aslan homeworld, worlds within the Imperium, and a bit on starship design. There is even some detail on the Aslan language, at least in terms of names.
For 44 pages it is pretty well packed. There is not a lot of "fluff" here, mostly all "crunch." So no fiction from the point of view of an Aslan mercenary or a human living on an Aslan world. Just the basics and enough to get you going on to your own adventures. Honestly, it is all you need.
This was the Alien Module I wanted the most back in the day. Researching it now I see that a lot of people did what I was going to do with it; mix in liberal amounts of Kzinti and some Caitian as well. Plus I was going to have psionic ability be a bit stronger in Aslan women. A nod to a lot of the scifi I was reading at the time. I also noticed just as many people complaining about others doing exactly what I wanted and described! Yes, the Aslan are fine just as they are but I also like my ideas too. Thankfully this book lets me do all of that.
Alien Module 2 - K'kreePDF. 44 pages, color cover, black and white interior art.
These aliens were very alien to me. While I could relate to the Aslan and the Vargr, these centaur-like aliens were very different and thus pushed a lot lower on my "wish list." I don't even think I had read any of this book until I picked up the PDF ten years ago.
This book is set up much the same as the Aslan book and the future books in the line. I found the bits on K'kree psychology most interesting. As herbivores, they tend to be peaceful (ETA unless you are a meat eater). This combined with the race's inherent claustrophobia goes to explain that while they had Jump technology they had not expanded as fast as other races.
We do get the sections on history, politics and governments, space travel and starship design, and the language section on creating K'kree names. There is a section on character creation as well.
This Alien Module also gives a few pages on adventures with or about the K'kree. So a little bit more background here than on the Aslan, but I think needed since this species is so different.
Reading this 10 years ago I was not overly impressed I think. Today I am of a completely different mind and would like to see these guys used more.
Alien Module 3 - Vargr
PDF. 50 pages, color cover, black and white interior art.
While I knew about the Vargr, they were the big three alien races GDW was advertising back in the day, my first *real* interaction with them was way back in the early 2010s when I was looking for new ideas for Ghosts of Albion adventures. I stumbled on one from White Dwarf #62, "An Alien Werewolf in London" about a Vargr in Victorian London. It was an odd adventure, but I gave it go for Ghosts and always wanted to try it again with Doctor Who Adventures in Time and Space.
This book is a bit larger than the previous two, largely because there is a lot you can do with these guys. Also they are the most fun in terms of history.
Vargr look like Terran wolves because generally speaking that is what they are. They were transplanted from Terra (Earth) to their homeworld by the Ancients over 300,000 years ago. Now 300k years is not enough to evolve any stock into something like the Vargr so they had been artificially engineered for intelligence and survivability. They share a number of physical characteristics of both humans and canine stock but have some minor differences as well. They still have the psychology of pack hunters following a charismatic leader and working in small, but somewhat unstable, groups. Pack membership can change and leaders can be followed or discarded at any time. This has had two effects on the Vargr. One their history is a confusing affair with no one narrative of what happened. Most of their 300,000-year history is largely unknown to them. Also it leaves them with no central government nor even any type of government that could be considered "typically Vargr." See why these aliens can be fun!
We get the now usual sections on character creation along with a brief language update for names. Some basics on the Vargr worlds and space travel.
We also get a section called "Gvurrdon's Story" which is given to us from the point of view of a Vargr.
This makes up the "Big Three" in my mind. I know more were introduced soon after (and I will get to them) but these are the ones I associate the most with Traveller.