Players have to juggle a dozen different resources in Age of Wonders 4. For instance, Gold pays for buildings and unit upkeep, Mana buys new spells and maintains old ones, and Research opens up new spells and tomes for players to use.
However, no resource is as useful to have or as hard to get as Imperium. Imperium gives players permanent boosts to their empires, allows empires to expand in different ways, and even pays for some of the best units in the game. The only problem is figuring out how to get more.
Where to Get Imperium
Every faction starts the game with +40 Imperium income. This comes from the Throne structure in the capital city, which also provides +20 Fortification to the city, +60 Knowledge, +120 Gold, and +20 Mana. Players can also get +5 Imperium by building each stage of the Wizard Tower, for a total of +20.
However, other cities in the empire don't generate any Imperium on their own. Instead, the only way to get extra Imperium is to annex Ancient Wonders or annex the Magical Material called Rainbow Clover. Every Ancient Wonder provides +5 Imperium regardless of its rarity or value, and each Rainbow Clover also provides +5 Imperium. Players must own the province to get these bonuses, but outposts are good enough to get a global resource like Imperium.
Cities, Vassals, and Units
Expanding the faction empire costs Imperium. While building an outpost has a small cost of 50 Gold, converting that outpost into a city carries a cost of 200 Imperium. Players can get a discount by building a new city on the ruins of an old one, but even then the Imperium cost is 100. Absorbing or Migrating a captured city also costs 200 Imperium, although Vassalizing costs nothing. This means that players who don't mind an Alignment hit and a few turns of waiting can raze a city and build a new one on its ruins to get extra Gold and save on Imperium.
Vassals have two ways players can spend Imperium. First, players can boost a city's Allegiance at the cost of 10 Imperium for each 1 Allegiance, although they can only do this once per diplomatic state. Second, players can spend Imperium to integrate a vassal and add it to the empire. Players can integrate vassals at the Flourishing Vassalage and Supreme Vassalage stages, and the exact cost of doing so depends on a few factors like the city's size and value.
Finally, players can spend Imperium on unit upkeep. Every tier 4 unit costs 3 Imperium per turn, and every tier 5 unit costs 7 Imperium. Affinities, summoning methods, and unit types have no impact on this cost, and it's universal for every high-tier unit.
The Empire Development Tree
The most common way to spend Imperium in Age of Wonders 4 is by buying skills and rites from the Empire Development Tree, which players can access using the big green button just beneath the Imperium counter in the upper-left corner. Players get access to skills on the Affinity branches by improving their Affinity scores, and the way to do that is to pick up new tomes of each affinity.
This guide won't explain what every skill in the tree is and does. Many of them are only useful in certain realms and scenarios, and players can always see for themselves what each skill does. However, there are a few universally useful skills players should always get when they have the chance:
- Expanded Governance: This General Empire rite adds 1 to the city cap each time players choose it. However, the Imperium cost also goes up each time.
- Teleporter Infrastructure: This General skill unlocks teleporters and similar province improvements, which can greatly reduce army travel times.
- Soiltenders: This Nature skill doubles the food income of farms from 5 to 10.
- Wild Expansion: This Nature skill spawns a new Animal unit on each annexed province. These animals can include tier 3 and tier 4 units.
- Casting Reserves: This Astral skill adds +20 Combat Casting Points and World Map Casting Points and only costs 10 Astral Affinity and 50 Imperium to buy.
- Lure of the Horde: This Chaos skill provides a 50 percent chance of spawning a tier 1 or 2 unit next to a victorious army.
- Military Engineering: This Materium skill reduces the outpost cost to 25 gold and 1 turn, and it gives new outposts a free Palisade that forces enemies to siege them even when empty.
- Metropolitan Society: This Materium skill boosts all city incomes by 10 percent if they border the Throne city.
Age of Wonders 4 is available now on PC, PS5, and Xbox Series X/S.