Ager Incognitus: A Tribal Land Overhaul
A Tribal Land Overhaul for Imperator: Rome
v0.2.3 beta — Compatible with Invictus 1.11
In vanilla Imperator: Rome, land is neutral. Tribal nations are defined by what they lack: research speed, city-founding rights, civilisation value. The forests of Germania, the steppes of Scythia, the mountains of Caledonia offer no particular resistance beyond a combat width modifier.
Ager Incognitus — Unknown Land — changes that.
Tribes are not failed civilisations. They are a different relationship between people and land. That land should be strong for them, and hostile to everyone else.
The mod operates on four interlocking systems: terrain that resists those who don’t belong, governments that reward knowing your land, populations that make conquest a long problem rather than a quick one, and confederacies that rise and fall the way history says they did.
Every province receives a permanent tribal density tier at game start, assigned by terrain. Fertile lowlands — Italian plains, the Nile Delta, Mesopotamia — are left as pure vanilla. The mod begins where administration genuinely strains.
- Marginal Interior — Hills, dry plains, forest. Tribal structures remain relevant alongside central authority. Hostile armies forage poorly; local populations do not cooperate with those they don’t recognise as their own.
- Remote Frontier — Marsh, jungle, desert. Tribal populations dominate local society. Hostile armies face serious attrition and find little to forage.
- Outer Marches — Mountain, steppes, taiga, desert hills. Beyond administrative reach. Hostile armies bleed and starve here. These are the lands that swallowed Roman legions and Macedonian columns alike.
Each tier increases hostile army attrition and degrades foraging specifically for armies that don’t belong there. The owning army is completely unaffected — the asymmetry is native to the stat, not achieved through compensating modifiers.
Tribal governments gain hostile attrition bonuses and reduced own-army attrition on top of the terrain system — knowing your land is a military asset in its own right.
- Tribal chiefdoms: +3 hostile attrition to enemies, −0.35 to own armies
- Tribal kingdoms: +2 hostile attrition, −0.20 own attrition
- Tribal federations: +1 hostile attrition, −0.10 own attrition
- Steppe hordes (Invictus): +2 hostile attrition, −0.30 own attrition
A tribal chiefdom in the outer marches is genuinely formidable. A Roman expeditionary force in the same province starts bleeding on arrival and doesn’t stop.
Taking tribal territory doesn’t end the fight. Non-tribal powers holding Remote Frontier or Outer Marches provinces with meaningful tribesmen populations face active resistance that scales with how many tribesmen remain and how difficult the terrain is.
- Restive Population: unrest builds, state loyalty drains, assimilation slows
- Active Resistance: serious unrest, pop promotion blocked, loyalty actively collapsing
- Tribal Friction: outer marches provinces with dominant tribesmen impose mild attrition on the occupying army itself — the population does not supply, guide, or support forces it does not recognise as its own
Restiveness applies and removes itself automatically as populations shift. A province held long enough, with sustained assimilation, eventually quiets. One reconquered by a tribal nation clears immediately — the land remembers who belonged there.
Restiveness effects can be toggled off for players who want the terrain and military asymmetry without the governance pressure.
When a tribal nation comes under direct attack from a Great Power of a different culture, confederation pressure builds. This is not a permanent buff — it is a gauge that rises under threat and fractures when the threat passes.
For AI tribal nations: pressure builds automatically. When it peaks, the tribe absorbs its strongest available kin-culture neighbours as military subjects, creating a genuine coalition. When the crisis passes, the coalition dissolves — the subjects are released, the chiefs return to their own hearths, the unity fractures back into clan loyalty. Exactly as Arminius’s confederation did after the Teutoburg Forest.
For the human tribal player: the full mechanic is in your hands.
- Threat on the Border — a Great Power is attacking. The clans grow wary. Low pressure applies.
- Call the War Council — spend political influence to formally summon the chiefs. The decision unlocks when pressure peaks and you are actively at war.
- Invite Tribe to the Confederation — repeatable. Each use absorbs one neighboring kin-culture tribe into your realm, largest first, at a PI cost. Choose which chiefs march with you. Their clans become yours for the duration — and beyond.
- The Confederation Dissolves — when the crisis passes, the unity fractures back into clan loyalty. The chiefs you absorbed remain part of your realm, but they remember they were not always. The stability cost of dissolution scales with how many you called: the larger the confederation, the heavier the fracturing.
Playing as Rome: when a neighbouring tribe reaches confederation pressure, your scouts send word — a visible intelligence event warns you that something is forming in the forest before the levy numbers confirm it. And if your frontier campaign goes badly enough, your legions come home carrying Frontier Exhaustion — five years of suppressed aggression toward tribal territory, during which the AI will naturally seek easier targets elsewhere. The frontier that cost you pushes back against another attempt while the memory is fresh.
- Designed for Invictus 1.11
- Additive on_actions chaining — nothing overwrites Invictus or vanilla hooks
- Compatible with Realistic Warfare Plus — RWP makes battles decisive; AGI makes tribal territory resistant to occupation. They operate on different parts of the warfare loop.
- Optional THA compatibility — tanist governments gain land_unit_attrition reductions without doubling THA’s existing hostile attrition values
- Does not modify hardcoded modifiers, pop types, or terrain types
- Invictus
- Content mods (missions, events, map)
- Realistic Warfare Plus (if using)
- Ager Incognitus (last)
- Dynamic density shifts — density tiers shift slowly over time with ownership, assimilation, and war. The land has memory: non-tribal occupation gradually erodes tribal character; reconquest restores it.
Ager Incognitus is inspired by three community mods — Tribal Homeland Attrition, Realistic Tribes, and Tribesmen Revival — none of whose code is used directly, but all of whom pointed toward interesting possibilities for increasing the strategic significance of tribes and tribal lands.
