A Caesan is often the first alien species encountered by the Xenonauts. They are physically frail in comparison to other species, but are still a dangerous threat. They are also the only race with psionic abilities.
Caesans are usually the first Alien species the player will encounter. They are the weakest of the main alien races physically, and are the easiest to capture alive.
Caesans make up for this by being among the more intelligent species, employing the usage of cover, flanking and suppression to attack human targets. As well as being one of the only alien races with access to psionics, which can prove devastating against human attackers.
Since Caesans are physically frail and not very adept in any field of combat, they will make smart usage of cover to mitigate incoming attacks, and attempt to flank the enemy. Their statistics are mediocre across the board with their only advantage being their psionic powers. Caesans are the only alien species that are comparable to a human in combat prowess.
One of the least known but most effective ways of dealing with Caesans is to give the best armor possible (not including the Predator armor), a shield and a stun baton. This seems like the best way of capturing enemies. The scout UFO usually contains around 3-5 aliens, and can be cleaned by two soldiers with the mentioned equipment, during two turns.
A Caesan stands approximately 170cm tall (5 feet 7 inches), with roughly humanoid proportions though a physically weak frame compared to human being. Caesan physiology is intriguingly similar to human physiology, however, there are several notable differences. An enlarged cranium provides a large brain cavity and a correspondingly large amount of brain tissue compared to a human. Though the circulatory and digestive systems are both recognizable, the fundamental method of oxygen transmission in blood cells is not hemoglobin as in humans but a similar (and more efficient) protein that we suspect is synthetic - this causes these aliens to have purple rather than red blood. While most internal organs are present or have an obvious equivalent, there are no signs of either the liver or either of the kidneys. Nor is there any form of reproductive organ.
Interestingly, genetic analysis of tissue samples from recovered corpses shows that there is only a single sex chromosome and, more importantly, that all recovered Caesans appear to be genetically identical - that is, they are all clones. All also possess atrophied vocal cords, allowing them to produce guttural noises such as groans and screams but not form words or communicate verbally. This leads us to believe that that these creatures have a telepathic link to one another - or perhaps something else has a telepathic link to them. There is little else we feel that can be gained from studying the dead creatures - capturing a live specimen would be an required before we could learn more. On a biological level Caesans are even more frail than humans are, so in combat the only advantage they gain will be from their superior technology. Detailed information on Caesan physiology has been passed to our troops, which should grant them a slight increase to damage in future engagements against these aliens due to a better knowledge of their weak spots.
Without the ability to communicate with our extraterrestrial attackers, there can be no peace. This war could only end with the extinction of one side - genocide on a galactic scale.
It is therefore helpful that study of our captive has yielded the secret of alien communication. Extraterrestrials have atrophied vocal cords because they communicate via radio telepathy rather than verbally; an alien "word"; is in fact just a short burst of radio waves. Energy-intensive, but effective. We have been able to construct a basic alien vocabulary by using our lab transceiver to record radio transmissions from our captive and repeating them back in various combinations. Study of the responses by our resident cryptographers deciphered the meanings of several, allowing us to conduct a basic conversation with our captive and expand our understanding still further. Though I care not for such trifles, our work here has created an entirely new scientific discipline - making me the father of xeno-linguistics.
It is a shame that our captive proved such a terrible conversationalist, endlessly repeating a request for new orders and refusing to engage on any other subject. Interestingly, it seemed happy to thoughtlessly follow simple orders issued by my team (such as moving across its cell). Eventually, once it had become clear that no more could be gained from questioning the creature, one of my team handed it a pistol and ordered it to kill itself. It promptly complied, splattering its brains across half the containment tank. It seems the alien soldiers are just mindless thralls; I suppose we will need to capture an alien officer if we are to get the answers we seek. Oh, and before you get too excited: reproducing the "suicide effect" on the battlefield is completely impractical (it requires a stationary target and laboratory full of equipment).
-"Caesan" most likely derives from "Caesar", the Roman General and dictator.