I recommend the deadly intentions series by Sovereign77x
There are certain parts of that series, certain dialogs even that I found to be really evocative in terms of building a "mood".. which isn't easy when you consider the tools a foundry author has to hand.
Also: I recall playing a mission a while ago called "Instruments of Armageddon" by Cheroj.
I had a few personal issues about the character development in the mission overall because i tend to invest myself alot in whats going on in the story. However!... the early section of this mission is a good example of how to build up a sense of dread for the enemy you're going to face.
There is a part where you discover your enemy's previous victims and the description just made me go "wait...WHAT THE HELL JUST HAPPENED HERE!!?"... it was really awesome writing