There is a fair amount of opinion around what a Blight is. For your purposes, a Blight occurs when creatures called darkspawn rally in great numbers around an archdemon and rise to the surface with the intent of destroying whatever they come across. An archdemon is an Old God, manifested in the form of a dragon. They do not accompany the darkspawn to the surface, but direct the hoards from deep below the surface. A Blight cannot end until the archdemon has been killed.

This has come to pass five times in recorded history, and hopefully shall not come again in your lifetime.

What you should concern yourself with are darkspawn, which are capable of tunneling to the surface and spreading disease and death as they travel. They are twisted figures, most stand upright on two legs and all ooze black from their eyes and mouth, and will bleed black if you manage to cut them. They are capable of breaking through to surface in smaller groups, though the threat of their presence should not be underestimated because they have not brought an army with them. You are likely to come across them in your time with Riftwatch. The wisest thing you can do if you come across darkspawn is run in the opposite direction, as attempting to fight one can either be your death at the end of their weapons or death from the taint, which spreads from contact with their blood. There is no cure for the taint, so please do not take the danger lightly.

[ a further note, scribbled along the bottom of the parchment: What are your suggestions as to what they should do if they can't run?