So, for example, when up against Habsburg Monarchy (Livestock Colony) Level 1+ and have both a "Jungles" card and a "Mountains+Wetlands" card in the Build Space, then (in order):
"Pressure for Fast Profit" (The Tsardom of Russia Level 6) and the "Invested Aristocracy" Event both add extra Invaders on boards where the Ravage Step added no Blight even if there was no chance to add Blight because no Ravage Cards were being resolved. (Fortunately, neither happens on Turn 1 – the latter because it can't resolve on Turn 1, and the former because it explicitly excludes Turn 1.)
"Migratory Herders" (The Habsburg Monarchy Livestock Colony Level 1) attempts to gather Towns even if no Build Card was resolved that turn. That being said, if there's no Build Card in the Build Space, this Adversary effect won't actually do anything because there are no matching lands to gather into.
"Mining Boom" (Habsburg Mining Expedition Levels 3 & 5) upgrades and potentially builds even if no Build Card was resolved that turn.
The "Voracious Consumption," "Ransack and Ruin," and "Visions Out of Time" Events all resolve their "After the Ravage Step" effects even if no Ravage Card was resolved.