Civilization and its Monsters, Part 1: CRs and CIV Scores

Monsters exist in fantasy adventure world, and everyone knows it. The average commoner may not know the finer points of specter vs. wraith or the save modifiers of a troll, but they have a general idea of how dangerous a creature is (i.e., it’s challenge rating), and the monsters, in turn, have a sense of how much danger a village, town, kingdom, or nation can tolerate (it’s civilization rating or “CIV rating,” I suppose?). Civilizations overcome lesser monsters, endure equal ones, and are themselves overcome by greater monsters. This applies to communities and nations, and the civilized areas they control, at a macro level. The wilderness, the dungeon, and the other planes of existence follow adventuring logic at a micro level.

Civilization rating grows by size. A village’s rating might be around CIV 1. They can deal with a few threats of CR 1 or less, but CR 2+ threats will usually overcome them. In mechanical terms, this is a question of what kind of monster a few dozen commoners with short bows and spears could deal with. 

A large village or small city might have CIV 5, able to manage a small group of CR 5 threats. A city-state or small nation with CIV 10 could tolerate a CR 10 threat, plus its minions and associated dangers. A very large and powerful nation or a confederation of nations might have a CIV in the mid- to high-teens. Only interplanar civilizations or cosmic organizations could hope to endure or overcome CR 20+ threats; these are generally things capable of ruling or ending the world, should they wish to do so. Adventuring tiers conform to these expectations. The classic high fantasy adventuring party that saves the village at 3rd level, the kingdom at 9th level, and the world at 18th level fits this scaling system.

Just as adventurers in a typical scene-based (e.g. non-dungeoncrawl-oriented) game may seek out monsters with a broadly applicable challenge rating, so monsters come into conflict with civilizations with CIV scores that would rival their CR. An adult dragon is generally going to find a city to be beneath its interest unless it's the capital of a kingdom, fabulously rich, or otherwise special; but a young dragon would find that same city an ideal target. 

A small number of 5E's standard monsters do better or worse than their CR alone would suggest. Low-CR shapeshifters and charmers like cambions, doppelgangers, jackalweres, hags, incubuses, and lamias punch above their weight, because they can influence or control others' behavior. Conversely, some double-digit CR brutes without a lot of mobility or special attacks can't threaten too big of a civilization simply because attacking individuals one at a time only goes so far.

Next: Civilization and its Monsters, Part 2: Rule and Ruin