Part of your role as ruler of an empire in Imperator Rome is to shape the laws and systems by which your society functions. And in this case you have three distinct approaches, as the history of the classical era dictates. Monarchy, republics, and tribes all feature unique bonuses and certainly bring their own challenges to your game too. Here’s how they work.
Monarchy is arguably the simplest government type, not least because your monarch rules for life. So if they ascend to the throne at a young age, you can be fairly sure of your leader, and thus your empire-wide buffs and weaknesses, for a long time.
That in itself brings about a bit of a headache when your ruler dies, though: the laws of succession dictate who ascends to the throne next. Usually it’s the eldest son of the family, so if they have particularly terrible stats, by default you’re stuck with those stats for as long as they life.
However, in a monarchy it’s easier to change laws than in other government types - including succession laws themselves. So you might find a way to avoid crowning a weakling king and instead nudge a family member with better stats onto the big chair.
Not everybody loves monarchy, as one might imagine given the skullduggery mentioned just above. You’ll always face a number of individuals from outside your family who would be monarch if they could just find a way to force their way in. These individuals are known as pretenders, and thwarting their efforts comprises a significant chunk of your duties when running a monarchy.
If they win loyalty from the public, they’ll lose loyalty to you. And that ties into the other crucial stat in a monarchy: legitimacy. Your legitimacy to the throne is affected by several variables, but importantly it’s diminished by public support for pretenders.
How might one stop this? Firstly philosophers can talk sense to your public and work that legitimacy stat back up, and secondly religious power (eg sacrificing to the gods) can be spent to boost it.
The most important stat of all for monarchs is charisma - all kings have to be popular.
Taking a radically different approach to monarchy, republics in Imperator Rome are based around a senate, which is an assembly containing 100 seats, divided into five factions.
At the beginning of the game, the split of these seats is equal between the civic, military, merchant, religious and populist factions. But as the game progresses this split changes, depending on each faction leader gaining or losing popularity with those 100 members of the senate.
The important skill for faction leaders is oratory - the better they are at speaking, the more likely they are to get your senators to see their point of view.
As ruler, you can boost any faction’s presence in the senate, but you’ll take a cost of tyranny for doing so. Tyranny is a stat you’ll really have to watch out for under a republic government system, and it ticks up when you perform a number of actions - most notably, trying to force actions or law changes through senate without support.
Every five years, the senate votes for a new ruler. This means it’s far more unpredictable than a monarchy, firstly because each ruler’s stats and their effects will last a shorter duration, and also because it’s hard to predict who’ll actually be voted in.
Whoever does get the vote brings in a unique faction benefit, eg military leaders granting armies and navies a +10% morale boost across your empire. In fact all factions provide a benefit except populists, who not only provide none but also make doing just about everything 10% more expensive. It’s important to stop them from being voted in, then.
Tribes work a bit like a monarchy in that tribal chiefs rule for life. That’s good for stability, and gives you consistent stats affecting your empire for a long period.
However, when a tribal chief dies, all the clan chiefs hold a vote to decide who should succeed them. They do this by assessing who’s the best fit for the job, essentially analysing stats and prioritising the martial and charisma stats.
A unique perk of the tribes system is that you’re able to control other clan chiefs’ armies as your own, without having to pay for their upkeep. However, their loyalty to you is always ticking down, since their allegiance lies with that clan chief.
A major downside, on the other hand, is that clans are highly resistant to change, and automatically lose 20 loyalty to you when you try to change a law.
It’s possible to convert tribes to monarchies or republics using the centralisation mechanic. By passing more centralisation laws that favour a move towards civilization, you’ll eventually face the opportunity to leave your barbarian ways behind. Conversely, you can actively move your tribes into functioning like more of a barbarian horde.
Tribesman like being in low civilization areas, unlike citizens, so you need to promote tribesman to citizens if you want to move towards centralisation.