Factions of the same race may choose to confederate into one faction if conditions between them are right. Confederation can be agreed via diplomacy. Confederation combines the two factions into one, and cannot be reversed.
Confederation incurs a public order and diplomatic penalty that will last five turns. You may not confederate again until this period ends, even if relations are good.
- Human and Dwarf, High Elf, and Dark Elf factions may confederate with their own kind if mutual relations are good.
- Greenskin and Beastmen factions are more likely to confederate if one is much stronger than the other, be it at high relationship or as part of a peace deal.
- Lizardmen factions will typically reject confederation options without a significant positive diplomatic modifier.
- Tomb King and Vampire Coast factions cannot confederate.
- Norsca has special dilemmas to help them confederate after they defeat a rival faction leader in battle.
- Brettonia has special techs which can force confederations
- The Empire have Fealty mechanics which can force confederations.
- While tempting, confederation should only be chosen if you can afford armies to cover the entire extended frontline and public order penalty. As such, always inspect the provinces being confederated into your empire before actually going through with the proposal. Bigger isn't always better. On the other hand, it can provide a significant boost in the late game and extend your reach if you confederate with a faction on the opposite side of the map and, say, the target of a lengthy war.
- Furthermore, all existing units and lords of the faction you confederate with come under your banner automatically.
- If you want to confederate with a faction do not give them a military or defensive alliance, this will boost their strength rating because it takes their allies (you) into consideration. It is not impossible to confederate with a military ally, as it guarantees high relations, but it is usually easier without an alliance.