The Early Age
flavor/intro text about EA
Magic sites are more common by default, though this can be changed in the game settings.
Population levels are lower. Specifically, each province receives a -20% modifier to their randomly generated population level, in addition to whatever modifiers they may receive from province size, terrain type, or any other map features.
Independent populations are less advanced and may use bronze equipment, but exotic types are more common. You will never find knights or crossbows, though you may find hoplites, cataphracts and war elephants. Amazons, barbarians, lizards, Zotz, Pale Ones, Ichtyids, Fir Bolg or even Trolls are more likely. Many of these will allow you to recruit some sort of weak shaman or priest, or various specialized units.
Certain mercenary companies and random events do not occur in the Early Era.
Early era nations are typically characterized by having more powerful, yet less versatile mages, being focused around powerful magic and sacred troops only available in the capital, and a lower level of technology compared to later eras. Nations are less often ruled by humans or near-humans, and instead are more likely to be ruled by living gods, demons, giants, or other supernatural beings. Few nations rely on or have good access to communions.
This lower technological level means that fortresses cannot be upgraded to a very high level, and some nations cannot build anything more advanced than a palisade. While most nations can still gain two command points from their fortresses, many of them have fort types with low defense values. No nation has access to crossbows, and heavy armor, two-handed weapons and heavy lances are rare. Nearly half the nations in the era use bronze or stone equipment rather than iron.
As with every era, there are nations which go against the general trend.
The Middle Age
The Late Age
flavor/intro text about LA
The Late Ages are characterised by:
High population numbers in provinces leading to high gold income and many blood hunting opportunities.
Many nations having access to blood hunters.
(on default settings) Low amounts of magic sites, therefore also low gem income
Mages tending to have lower maximum path level, but wider different path access.
Crossbows everywhere, I am not joking.
Tribes are rather rare as indie pop types, getting a N1 mage recruitment from them can not be guaranteed. On the other hand scouts are plenty available.
R'lyeh is the only true underwater nation remaining.
High level forts, citadels are widely available.