Not playing as a released vassal.
The player’s country:
- is an elector of the Holy Roman Empire.
Starting as Hesse is recommended. For this achievement, it is best to border a weak elector (e.g. Mainz). The goal is to fabricate a claim on the elector while at the same time securing an alliance and possible royal marriage with Austria (or the present Emperor). Declare war and annex the weak elector, and release them as a vassal immediately to remain small. Since one elector is gone the Emperor will try to appoint a new one and if the Emperor's opinion of the player is good enough, they may grant them the position of elector.
Another method is inheriting Bohemia, which starts as an Elector and in an interregnum. Marry Bohemia on game start and wait until the player's dynasty rises to their throne, then claim their throne immediately and press the claim. Secure a Personal Union and wait. After 50 years there is a chance to inherit personal union junior partners on monarch death, and when this occurs the player will become an elector. Austria can also easily secure a personal union over Bohemia through the 'Secure Electors' mission, which grants a Restoration of Union CB.