So, I have read and re-read the rules on building the dice pool and there doesn't seem to be a lot about when to use challenge dice. It seems besides opposed skill checks, if the npc has training, or spending a dark force point there really isn't any other way to use them and you should use set back dice instead of upgrading difficulty. The side bar on page 21 seems to say once difficulty is set, if circumstances would make it harder use setback dice.
Since despair is only on the challenge, I'd like to be able to have them in play when appropriate.
So, I wanted to ask the community when else do you use red challenge dice?
Thanks