Just what it says on the tin. Say, instead of marrying Sophia of Halshany, Wyadyslaw II Jagiello marries Elizabeth of Luxembourg. Effects? Could Jogaila swing the election to King of Hungary with Sigismund's (posthumous) support? Could we see almost a medieval Intermarum, with Jogaila in charge of Lithuania, Poland, Hungary, Bohemia, Silesia, Brabant, and Luxembourg? Could we even see the Jagiellons, instead of the Habsburgs, become de-facto hereditary Holy Roman Emperor? Could we see a Poland-Lithuania-HRE emerge? How huge can our Jagiellon-wank get?