- required >50 relations. It slowly (turn per turn) assimilate vassal ( unlike demand annexation that need to assimilate after annexing ), it cost diplomatic point and money depend on vassal size (population).
Coalition ( I know about coalition in trade)
- Temporary alliance of few nation against large nation that have -50 relations with those nation, disband after war.
- Interfere in war ( take side, occupied province automatically transferred to the nation that you take side)
Holy Roman Empire
- HRE Emperor
- Grant / revoke electorate (+/- 20 relations)
- Invite nation to HRE ( nation must be weaker than you )
- Non HRE member
- Disband HRE ( HRE emperor and elector province is occupied )
- Add 'threat' (-20 relations) to nation that being conquered by you. -10 relations to nation that was at war. -20 relations to nation that you have their core. Nation that have HRE province get -20 relations to all HRE members.
- HRE Emperor get +1 diplomatic point every turn.