Wall of fog

By casting wall of fog, the wizard creates a billowing wall of misty vapors. The wall of fog obscures all sight, normal and infravision, beyond two feet. The caster may create less vapor if he wishes. The wall must be a roughly cubic or rectangular mass, at least 10 feet across in its smallest dimension. The misty vapors persist for three or more rounds. Their duration can be halved by a moderate wind, and they can be blown away by a strong wind.

Note: This version of wall of fog originally appeared in the 2nd Edition Player's Handbook for Advanced Dungeons & Dragons from TSR. Its use here is for the purposes of providing context for the campaign only.