How to create a scary atmosphere

[Adny]

Can you guys tell me a little about particles? Like fog.. about when to use them and stuff.

Depending on the environment, fog & light dust will be most commonly used. For light dust, use it near light sources & disable "fade at distance" (something like that, it's a check box). For fog, color it lightly to match the environment, and set the distance settings to:

min in: 4
max in: 5
min out: 10
max out: 20

If the fade in distances (above) are set correctly, even if it clips through walls, the player couldn't really see it. If you need it to be even lighter, set the alpha value to 0.5. The aforementioned values are pretty much default, therefore will be need to changed and tested in game very often.

Hope that helped.