From Solium Infernum Wiki
This action allows you to demand that an opponent give your resources. The resources can always include tribute cards. If you infernal rank exceeds the targets, your second demand can include cantons, and you third can include artifacts and relics.
The opponent can choose to refuse or concede to your demand. If they refuse, they will gain the same prestige it cost you to make the demand. You will then gain the option of claiming a vendetta, which if you win, will generally cover the prestige loss of the initial demand.
If you opponent concedes to your demand, you will be prevented from making another demand for some turns. If your rank is equal or higher, it will be 2 turns. If it is lower, it will be extended by one turn for each rank difference.
If you are at your initial 10 prestige, before making a demand, you should consider if will have enough prestige left to pay for claiming a vendetta. If you spend 6 prestige on a demand and the remaining 4 on the vendetta, you may find yourself winning the vendetta, but only having 8 prestige as a result (and your opponent will probably gained 4 overall). To avoid this situation, you may wish to gain a few extra prestige initial by capturing a place of power, buying a relic that grants prestige, or hurling insults.
This action allows you to openly insult an opponent. If they accept the insult, they will lose some prestige, and you will double your prestige wager. If they refuse, they lose nothing, you gain nothing, and they MUST claim a vendetta. As usual, they can choose a war of legions or praetors.
Note: They can claim a vendetta even if they have nothing to wager. That means there will be no reward for winning or losing, but it will still open up the ability to attack each other if it is a traditional vendetta. If they do not wish open battle, they can claim a praetor combat, not show up, and not lose anything.
Send Emissary Bearing Gifts
This action allows to you send tribute to an opponent, in exchange for them not being able to make demands of you for some turns (1+number of cards+rank difference if higher).
The opponent my accept, refuse, or humiliate. Accepting lets them keep the tribute and will prevent them from making demands and insults. Refusing means there is no change for them and you get the tribute back, but you will still lose the prestige used to send the emissary. Humiliating means they gain some prestige, but you have the option to claim vendetta. If you win this vendetta, you gain additional bonus prestige for exacting your revenge.
Petition for Blood Vassal
This action requests that another player becomes your blood lord. The are a number of conditions that must be met before the option becomes available and becoming a blood vassal will significantly change the game for you.
The player you petition can accept or reject your petition. Typically you will have already worked out an agreement before making the petition. There is no penalty for being rejected (other than wasting the prestige and order slot you used for making the petition).
Conditions for petitioning for blood vassal
- Vassal must have less then 1/2 the prestige of the lord at the time of the petition.
- Vassal must have less than 1/2 the cantons of the lord at the time of the petition.
- Vassal and lord must have cantons that share a border.
- Neither player can be a vassal or lord already.
Once the petition is accepted
- The blood vassal will lose 50% of their prestige.
- The blood vassal is demoted to to the rank of lord. If the blood vassal was already a lord, they will continue to be rank lord.
- The blood lord will increase their rank by 1. If the blood lord was already rank prince, their rank will still go up! However, their are no additional titles, so they will continue to be listed as a prince. In this case, the improved rank will not be directly visible, but the higher rank will be used in all calculations.
- The blood vassal can no longer instigate or be targeted by diplomatic actions. However, any diplomatic state the blood lord enters in to also applies to the blood vassal.
- The blood vassal can no longer become regent. The regency passes over them to the next eligible player. This also has the side effect that the blood vassal will no longer draw new event cards.
- The blood vassal and blood lord can move freely through each other's territory.
- The blood vassal's and blood lord's legions and places of power may support each other in battle.
- If either the blood lord or vassal are excommunicated for ANY REASON they with BOTH be excommunicated. Watch out for the Event#Expel_the_Heretic.
Things that don't change
- Being a blood vassal does not protect you from conclave decrees. You must still respond to all events and can be targeted by events that effect things like your legions, cantons, or places of power.
- Blood vassals still have a prestige rating that can go up and down. They can gain or lose prestige from combat and destruction rituals and other actions. The blood vassal's prestige will be added to the blood lord's if the relationship survives to the end of the game, but if they are excommunicated and then granted amnesty via Event#Writ_of_Rescindment, the former blood vassal will once again be competing with their own prestige.
End of Game
- The blood vassal's prestige is added to the blood lords. Prestige from the blood vassal's cantons are included in this prestige, but any of the blood vassal's objectives (secret or public) are ignored.
- If the blood lord is selected as the new lord of hell, the blood vassal is automatically selected as their lieutenant. Note that if someone else has the Kingmaker perk (and selected the blood lord as their target), they become the ruler of hell, not the blood lord, and the blood vassal will get nothing.
This action is available the turn after you didn't claim a vendetta when an opponent refused a demand. It is also available if an opponent has conceded to three demands in a row.
Claiming a traditional vendetta allows you to use your legions and rituals to attack on opponent. Claiming a praetor combat will limit the conflict to just the chosen praetors.
Each traditional vendetta you claim will have increasing minimum (and maximum) goals. It is possible the the minimum destroy X legions option has X set to a higher number than they have legions. The may also be true for places of power and cantons, although if you capture all their cantons, you can attack their stronghold.
Declare Blood Feud
This action is available after you have won a sufficient number of traditional vendettas (usually three). Praetor combats and vendettas that you lost do not count. I also do not believe that stopping a player from winning their vendetta counts (but could use verification).
Blood Feuds will last the remainder of the game and will allow you to directly attack each other's strongholds.
Note: You do not have to have started the diplomatic sequence to have a vendetta count. If someone insults you, and you respond by refusing and declaring a traditional vendetta, which you win, that would count as one of your three wins. It also does not matter what win condition you picked. Capturing territory is just a valuable as capturing a place of power or destroying legions. But again, praetor combat does NOT count.
Assertion of Weakness
Available in the Rectification expansion, this diplomatic action requires one previous insult to have been accepted by your target. Select an unoccupied border canton; you must seize that hex immediately on the turn following the Assertion and then hold it for a set number of turns.
The attacking player may not move into any other cantons owned by the defender and may not use any rituals they would not otherwise be able to were the relationship neutral. The defending player may likewise not move into or assault any of the attacking player's cantons except for the one he declared. However, the defending player MAY use destruction rituals etc on legions that occupy the contested canton. If the defending player re-takes the canton at any point before the turn limit, the Assertion fails.
Once an Assertion has been made (win or lose), the 'accepted insult' requirement is reset and must be completed again before another Assertion can be used.