The 1 Blight normally added by dealing 2+ Damage to the land in Ravage;
Blight added by cascades, including both cascades caused by an unusual condition, like the "Fragile Sands" effect of the Varied Terrains scenario, and "chain" cascades caused by cascading into a land that already has Blight;
Blight added by the Ravage due to the Invader Damage meeting a particular condition (e.g., The Kingdom of Sweden's "Heavy Mining" check).
However, it excludes:
Blight added by a separate action "After" the Ravage Action, like from The Kingdom of Scotland's Level 5 "Runoff and Bilgewater" effect;
Invaders in The Endless Dark block a Terror Level victory.
Presence in The Endless Dark prevents loss from Spirit elimination.
Beasts in The Endless Dark count towards preventing a loss against the Tsardom of Russia.
Towns in The Endless Dark count towards a loss against the Kingdom of France.
Presence in The Endless Dark can be destroyed by Events and Blight Cards that destroy Presence from each Spirit (but not those that destroy Presence from specific boards).
The Endless Dark does not count for loss conditions that are based on contents of a particular land, like Habsburg Mining Colony or the Kingdom of England.