Yeah, Red Fog just gives your guys a permanent -15% chance to hit. I guess that's sort of an extra hard challenge mode?
I actually lost a Terror mission against Chryssalids this morning. First Terror mission of a new campaign, and I went in feeling pretty good. I already had a Lieutenant Sniper, Sergeant Support, and had two Corporals with me. Heavy and Assault. The Assault and Support had laser rifles.
So, of course I get a nice huge Government building where my squad sight sniper is pretty much useless. I figure I can sort of make it work by using his pistol since he has gunslinger.
Well...the game decided to be evil. First Alien turn and Two groups of Floaters and a Chryssalid pack show up. I take out one Chryssalid, but the other scampered off to somewhere in the building I can't see.
The Floaters keep me pinned down for a while. They didn't hurt us, but they tied us up long enough for the Chryssalid to start making zombies. I was then tied up with a never ending wave of zombies while that bastard ran around making more. I even got to shoot him once, but he didn't die.
In the end it was just too much. A zombie came around a corner and one-shotted by Heavy early on, and he was my best chance against this situation with bullet swarm. With him gone, it was a lost cause. I just didn't know it yet. I'm slowly pushed back into a corner, well away from the Evac zone, with zombies and Chryssalids swarming everywhere. We took out 12 of the bastards, but they just keep coming in waves. And zombies can soak way too much punishment with Damage roulette on. Didn't help that my assault missed a 90% shot early on that might have let me turn the tide.
*sigh*
Still, it was interesting watching my guys get zombified. And I was amused that the Assault, the guy with the lowest Will by far, never panicked during that mission while my awesome sniper with a high will did.