PTMC Directive CMD-HR151 580
To: MD1032, Mercury Orbit
From: PTMC Headquarters, Earth Orbit
An unexpected development has arisen. What we once thought was childish has reached us from afar. An unexpected being that might threaten your paycheck is waiting.
Prepare for descent.
Fans of MLP say: "If it exists, there's pony of it." To which I respond: "Hey, fan workers! You missed a spot!" 
Interplay and Parallax's Descent series were among my favorite computer games growing up in the 1990s. I looked around recently, and I didn't see any crossovers between the two, whether it be stories, art, anything. Couldn't have that, could I?
(Addendum: It's been pointed out to me that there is, in fact, pony artwork of Descent in existence already. Shows what I know! 
)
A one-shot deal that came about after I learned of Volition shutting down. Timeline-wise, this takes place in the middle of the first game (Descent) and at some point between the last two episodes of Season 9 (MLP).
And no: to curtail any questions on the topic, I won't be continuing this. As of this date (Sept. 22, 2023), just writing this was enough of a distraction from M.L.G. as it is.
The cover image is from Descent II's intro cutscene.
Oh really? Then you missed a spot, because, in terms of art, I've got you beat by about a decade. Not even exaggerating with that--I posted that in February of 2013 (good grief, it's really been that long?)
Anyway...Descent and MLP don't exactly pair naturally, and mix that with the fact that Descent has (sadly) become a bit obscure for the current generation and you get why there hasn't been more crossover content. Heck, I was pretty darn shocked to see this fic in the new fics list at all because of all of that. Still, you did a pretty good job here, even if the justifications for getting Marmalade into the cockpit was a bit of a stretch even for the PTMC (and yet still so very in character for them
), so I'd say it all worked out better than I expected going in. 
I had not heard Volition was shutting down. Sad but admittedly not surprising--I'd heard their past few releases hadn't been super successful, and what with all the blows the economy's taken in the past few years...well...in any case, it is what it is sometimes.
...Well then, I've been looking in the wrong places, then. Thanks for pointing that out to me!
Descent... now there's a name I haven't heard in a long time. A long time.
I remember Descent: Freespace and Freespace 2 quite fondly. Never had Descent or Descent II, though. I didn’t control which games I got in those days. XD
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The Freespace games technically aren't part of the same universe as Descent anyway--the first Freespace game only used Descent in the title (and only outside of Europe, as in Europe it was titled Conflict: Freespace) so to avoid potential trademark issues with other software on the market at the time that also used the "Freespace" term.
Both are still good games in of themselves though!
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I've heard of the Freespace games, but I never actually played them.
The bigger-named games of the 90's---stuff like Descent, Star Wars: X-Wing, the original Command & Conquer, etc.---that I liked and enjoyed were due to my older brother's influence. He'd bring the games home, play them where I could see them, and I'd be taken enough with them that I'd start playing them myself. I imagine if it weren't for him, I'd have missed out on a lot.