lets talk about the akavir for a moment. i have read Mysterious Akavir;

it says that no men or mer live there, men once did however. Let's cut the bullcrap son. is this revisionist history to scare little children, or are these folks chimera beasts things?

if it is historical derp, then anyone know what the Kamal look like? i mean, what is a snow demon? why are the "races" so varied?

And what about the Tsaesci?

are they really immortal? some potent mate apparently was doing stuff to the empire for a few hundred years. amirite?

edit: i forgot to ask what Yokuda has to do with the Akaviri? if anything, i'm a little confused on that point.

Mysterious Akavir is pretty much about as canon as The Real Barenziah, to be honest. It's got grains of truth, but it's mostly a big steaming load of [censored]e. And to top it off, we don't know which parts are true, and which parts are [censored].

The Tsaesci might be literal snakes, or they might be humans. Maybe they've got legs, or maybe not. Maybe the humans were their cannon fodder, and the snakes were the generals. Or maybe they're a race of serpentine Tongues with access to a "Human Aspect" Shout. Maybe they're immortal, or maybe they're just incredibly long-lived.

As for the other races... there's even less to go on, and not a single description anywhere at all.

Tescani are almost certainly some type of human-snake chimera thing (with speculated shape-shifting abilities). As it is, the Tescani themselves tried to invade Tamriel in the late 1st Era and were defeated by Reman I who they then joined forces with. After the Reman Dynasty was assassinated, a group of Tescani ruled the Empire for nearly four and a half centuries until the Dark Brotherhood wiped them out. While we (the players) don't know for sure what they looked like, well researched literature has always used human and snake terms to describe them, nothing else. So no, people probably aren't purposely lying about what the Tescani look like.

Also keep in mind that Tamriel has it's own beast-folk with the Kajiit and Angorians. Monkey-people, tiger-people and snake-people aren't that much of a stretch by Tamrielic sandards.

Tsaesci are supposedly serpentine-like, however it is known that more human looking Akaviri were present during the First Invasion from Akavir. For this reason, it is sometimes speculated that the Tsaesci did not literally eat the humans but instead absorbed them into their empire. However, it is also said that the Tsaesci, being vampiric, may actually take on the form of what they feed on, and for this reason, many may have taken on the form of humans; this theory being backed by http://www.imperial-library.info/content/tsaesci-creation-myth-and-we-ate-it-become-it(you need only look at the name to get the gist of the source).

As or their immortality, both Versidue and Savirien ruled for over a hundred years (Versidue actually having been in Tamriel for over 600 years seeing as he came to Tamriel during the invasion), both of these snakemen did not die from natural causes. It can be easily said that the Tsaesci, if not immortal, probably have an extremely long lifespan.