Physical appearance and structure:

Senses:

Speech:

Society and customs:

Attitudes:

Special Abilities:

Comments: In our campaign Vrusks don't have 8 legs and 2 arms.  They have 4 legs and 2 arms.  This maintains integrity with vehicle sizes and space, for obvious reasons a lot of "mechanics" or "reality shifts" needn't be contemplated; i.e., imagine a centaur, essentially what an 8 legg'd Vrusk is, in a canoe compared with a human - whereas a 4 legg'd bug doesn't involve a mental leap of faith. (Or does it!)

Tetrarchs haven't died out.  They are essentially reclusive souls with technologically enhanced life-spans.  They live a dog-gone long time, only
to get together to procreate, etc., once every millennia or so.  Their ships are massive, one-"man", fully-automated behemoths that go about their
arcane business.  Somewhat reminiscent of Ents from the Lord of the Rings, they're slow and methodical.  They have bodies similar to large
land tortoises without the shell, hermit crab eyes and two 8 foot tentacles for manipulation.  They move through a series of tunnels and shafts in
their ships, which are forever being added to, much like the shell of a hermit crab which gets larger with age.  Thus, the larger the ship the older
the Tetrarch.  These ships are fully automated and serviced by a virtual army of robots and an arsenal of technological goodies.

The Sathar are motivated by the following intentions, which the PC's don't know:  They follow a devoutly religious regimen of some militaristic
ideology, which states to die in battle is divine.  They believe that this ideology is the only way to attain "heaven" or "salvation" or
what-have-you.  Those who don't follow this ideology are eternally condemned to die spiritually and are unaware of their collective, respective
condition.  Their only means of salvation is to be immediately killed in combat.  The Sathar believe it is their moral duty to purge the galaxy of
unbelievers, thus ensuring salvation for not only the Sathar but all others that are killed in combat.  They therefore make war on all others.  Those
chosen for this mission are the greatest priests/warriors of the Sathar cult and are indeed missionaries sent on holy work.  Their job is to kill and
then to commit suicide as they will have inevitably been contaminated with consorting with unbelievers, a contamination that mustn't be allowed
into the Sathar proper.  They are actually do-gooders, "spreading" the word - a sort of Jehova's Witness if you will.  Capture or surrender is the
gravest sin possible.

This, incidentally, was a theme of a fighter-type I PC'ed in D&D.  He was actually Lawful/Good but killed virtually everything in sight!  He was
extremely difficult to play and keep in character, very challenging.