Well I didn't have anything in mind in particular, although a few things have come up
since I remembered some old stuff.
In the case of this Demon Pirate Destroyer class ship, the fog ties into their creation
and mythos. Demons were explorers or fighters that got stranded, captured, and experimented
on in the mind altering twilight fog by Randall Cassitor.
The fog generator was destroyed in one of the Tachyon missions, so aid efforts were launched
to help the victims. Nothing says everyone wanted help though. That generator was 8th of a freighter sized ship
or so if I remember right... bit larger than a fighter sandwich. It produced a whole sector worth of fog.
So it's reasonable to assume you could mount some to a ship as a cloaking device, or simply a way to
scare people away, or perhaps it strengthens the aggressiveness of the pilots.... ie being high on fog.
Perhaps it scrambles radar and other instrumentation except on Demon ships.. etc etc... need I go on?
Without the right ship cards, some fog in tach ate your ship. Reducing the shields and hull until you left or blew up.