You call that a good idea? You haven't even addressed who/what the 'big bad(s)' would be, and how in god's name you would make them remotely interesting. I know XVI is a fantastic villain because it's humanity's worst nightmare; an implacable, faceless horror that turns people against their own kind, changing them into ghastly perversions of what they used to be.
So, yeah, whatever. Show me something less 'redicolous' than XVI and we'll talk.
Regards,
Winter
Less redicolous?
Anything. Dr. Insano would be less redicolous than the XVII virus.
You're kinda...mixing genres that shouldn't be mixed. Implacabe, faceless horrors are..well...horros. Undefeateble, etc.. I played The UFO series, and I don't recall implacable, faceless Eldritch horrors there.
It comes off as you yourself don't know what you want. You want a faceless horror in a tactical Sci-Fi game? That would be a poor choice from the start, for multiple reasons. This type of game doesn't lend itself well to pure horror (a FPS or adventure type game would be better), partially because of the premise of researching and finding out, analyzing and having heavily armed commandos killing shit and winning.
Part of the horror comes from mistery. And if you find out everything there is about the enemy, he loses a lot of the scary factor.
Well, a virus for one isn't a eldritch abomitation. It's a virus. Faceless tough it may be, it's got no intelligence. But you want some "evil" behind it. So you make it intelligent (stupid as it is)...and psychic (even more stupid).
You seem to think aliens can't be scary enough or strange enough. Well, that shows your failing as a writer, rather than the impossibiltiy of the concept, because truly alien and scary aliens have been done before.
But now I'm going off the tangent.
XVII virus as it is isn't "interesting" as you put it. It's just stupid.
As to who the enemy would be...do you need me for all the answers? You're supposed to be the great writer here, surely you can come up with something to fill in the gaps..But very well. Let's try something, off the top of my head...
So the Alien empire was formed when race X started subjegating other races. It expanded and conquered and soon fell upon the homeworld of race Y. Y was outclasses and was loosing, but they were a race gifted in bioengineering and has psychic powers. So they crafted the virus that would alter the targets brain, making it highy succeptable to psychic suggestion. The virus worked wonders and soon race X became slaves to Y.
From here on you can get creative in multiple ways. Maybe the virus backfired and started affecting race Y, driving them mad. Maybe Y became paranoid and determined to conquer any other race that could possibly harm them?
And maybe, the creators of the virus are simply unknown, their agenda unknown. Would leave thing open for a sequel and gives the air of mistery.
There's doezns of ways one could handle that.
EDIT:
I also noticed you haven't bothered to address point 1, about the huge power disparity.