as long as the Protestant faith is not enabled, the ruler of the HRE is only King of the Romans (King of the HRE) after the election and has to be crowned by the pope to become emperor
there is a decision to make the King of the HRE travels to Rome to be crowned emperor and there is a chance that he dies on his way or that the pope refuses it
the ruler of the HRE is able to declare war on the Papal State to raise an antipope and replace the current pope with that one
the CB is available, as long as the Protestant faith is not enabled, the ruler of the HRE is not the Curia Controller and he has invested the most or second most papal influence
if the ruler of the HRE is not emperor already, he will be crowned emperor afterwards without having a chance to die
under specific conditions the country with the most elector votes gains a CB against the current ruler of the HRE
the attacker with this CB can use a peace option to become Holy Roman king / emperor himself, if he has the most electors voting for him it costs less war score and gives no AE
the defender with this CB can use a peace option to imprison the ruler of the attacker, which will give the attacker a CB to liberate him (but he can also be released by decision)
the ruler of the HRE can invite Catholic, Protestant and Reformed HRE neighbor countries (neighboring a HRE province) to the HRE
if the country accepts, all its provinces are added to the HRE
if the country declines, the ruler of the HRE will gain a CB to force the country to join the HRE (peace option will cost half the war score that vassalization costs)
the ruler of the HRE gains a CB against rivals, enemies, heretic countries (if the HRE has an official faith) and non-elector kingdoms, which are members of the HRE and have less provinces than the ruler of the HRE, to ban them from the empire
the ruler of the HRE gains a CB against slavic pagan HRE neighbor countries (neighboring a HRE province) to convert them to the Catholic faith, as long as the current age is an age of the Extended Timeline Mod before the Age of Discovery (with the Emperor DLC this depends on an Imperial Incident)
Catholic, Protestant and Reformed HRE neighbor countries (neighboring a HRE province) can ask the ruler of the HRE to join the HRE
the ruler of the HRE can enact the Golden Bull within the Late Middle Ages (Extended Timeline), Age of Discovery and Age of Reformation (with the Emperor DLC the Golden Bull is an Imperial Incident, otherwise it's a decision)
this will restrict the prince-electors to be 4 secular princes and 3 ecclesiastical princes of the HRE and will reduce imperial authority, if there are too many electos of one category
this will disable the CB to declare anti-king
this will increase the imperial authority with 5
emperors can not be female and the "Pragmatic Sanction" is disabled
this will increase the opinion of all electors with 35 and all other members with 10 for a short amount of time
the Golden Bull gives the following bonuses til "Erbkaisertum" is proclaimed:
emperor: +0.05 imperial authority (requires 7 electors), +10% improve relations modifier, +0.25 yearly legitimacy
electors: +12 tax income
HRE members (not emperor, not elector): -1 national unrest
the ruler of the HRE can abolish the Golden Bull after the ruler that enacted it has died
this will remove all restrictions, maluses and bonuses of the Golden Bull
this will enable the CB to declare anti-king again
this will decrease the imperial authority with 10
emperors can be female again, if the "Pragmatic Sanction" was enacted before the "Golden Bull", otherwise the "Pragmatic Sanction" is enabled again
this will decrease the opinion of all electors by -50 and all other members with -10 for a short amount of time
Around every 3 years (it's an MTTH, so it may vary) one member of the HRE gets an event to host the Diet. Here he can choose between 3 possible proposals. After he picked one, the other members can agree or disagree to it. When all members have voted, the emperor gets an event to publish the outcome. If more votes agreed, the proposal is accepted and its effects are applied. Additionally the host gains prestige and the emperor gains imperial authority. If it's rejected, the host loses prestige.
When an emperor is elected, he gets an event to choose his imperial agenda. This is a small task he has to complete during his reign. Similar to estate agendas, if it's completed, a bonus is applied (not automatically tho, it is a decision). If the ruler dies before he can complete the agenda, the malus is applied.
In the ages in ET before the vanilla ages as well as in the Age of Discovery when a new emperor is elected, he will get decisions to grant the princes and electors privileges. These are basically a buff for those and a malus for the emperor. The emperor can also decide to not grant a privilege, however that will reduce the authority gain drastically.
The Slavic Threat
can only happen in the ET ages before the vanilla ages
can lead to the CB against slavic pagan HRE neighbor countries (neighboring a HRE province) to convert them to the Catholic faith
Investiture Controversy
can only happen in the ET ages before the vanilla ages
can have a pro-emperor (weakening the emperor's papal influence), pro-pope (weakening the emperor's imperial influence) and neutral outcome
Peace of Augsburg
can happen before the League War
The Hussite Question
can happen after the Protestant side won the League War
allows another large war to turn the official religion of the HRE into Hussite
A Foreign Emperor
can happen if the current Emperor is not part of the HRE
allows the Emperor to join the HRE at a cost of some maluses or give the Emperorship to a strong HRE member
One Empire - One Faith
can happen if the Emperor has a Christian faith, the HRE has a religious peace and the Erbkaisertum reform has been passed
allows the Emperor to maintain religious peace or make his religion the official faith of the HRE
during the HRE league war the emperor can transfer the electorship of a hostile elector to a league friend, if the elector is defeated enough
if a country is not an elector, but has a personal union that is an elecor, it will receive an event that allows the country to transfer the electorship of the personal union to itself
changed the flag of the Holy Roman Empire nation
changed the map color of the Holy Roman Empire nation to white
the emperor can Demand Reichstürkenhilfe, if he is at war with the muslim Ottomans and didn't demanded it within the last 10 years, which will give him 50 ducats per HRE member (except himself) and will change all HRE members' opinions of him by -20
after the "Gemeiner Pfennig" reform was enacted, the emperor can get an event to charge additional taxes (once per ruler)
most useful bonuses from the Imperial Reforms will still apply after uniting the HRE