ToME: the Tales of Maj'Eyal

I finished off the sandqueen and a corrosive vapor going. I went downstairs and rested several hundred turns to heal up. I went back upstairs to finish off the summons and get the prize. My corrosive vapor was still going! Everything seemed to freeze in time, because it was not hurting the worms in the vapor.

I've noticed this as well, and what is happening is the effect is gone but the image still has to time out for the talent's duration. It SHOULD disappear when you are on the level that the cloud effect is on once it's normal duration has passed.