So, the Hohenstaufens were first elected as emperors in 1138 (Conrad III), and the dynasty died out roughly 130 years later (in 1268) when Conradin (three greats-grandson of Conrad III's younger brother) was executed (although they'd lost the imperial title in 1254 already). In that time, they had climbed from dukes of Swabia to being Holy Roman Emperor, king of Italy & Sicily, king of Jerusalem, and arguably, the most powerful men in Europe. They likewise held the titles of count of Burgundy and one was married to the heiress presumptive of Spain, while another was betrothed to a Hungarian princess and still another to a Dane.
The Luxemburgs are a similar story. Count Henri of Luxemburg, a ruler of a reasonably small state in the empire was elected as emperor in 1308. Emperor Sigmund of Luxemburg (his great-grandson) died in 1437, holding the titles of Holy Roman Emperor, king of Bohemia, king of Hungary and Croatia, and other members of his family had been margrave of Brandenburg (which he himself had also held) and of Moravia as well duke of Luxemburg.
The Habsburgs, on the other hand, had their first member elected in 1273 (Rudolf I), lost the imperial crown in 1308 (Albert I; although Friedrich the Fair held onto the German crown a bit longer (1330), got their next shot at the imperial dignity in 1437. This time proved more lasting, since with the exception of one reign in the 18th century, the Habsburgs (or Habsburg-Lorraines) ruled as emperors until the dissolution of the empire, amassing titles like king of Spain, Naples, Sicily, Sardinia, Hungary and Bohemia, duke of Burgundy, Milan, etc etc.
The Hohenstaufens and Luxemburgs burned bright for about a century before going extinct in the male line. The Habsburgs, however, managed to stick it out for the long haul. The challenge, should you accept, is simply this: pick a date - 1273 or 1437, and let the Habsburgs only last a few generations (both Hohenstaufens and Luxemburgs were on the throne for 130 years - interruptions aside in the latter case - so that would be 1403 for a 1273 date or 1567 for a 1437 date) on the imperial throne before going extinct. But there's a catch. Since both other dynasties (Hohenstaufen and Luxemburgs) held kingdoms outside the empire (Sicily-Jerusalem for the Staufers and Hungary-Croatia for the Luxemburgs), the Habsburgs need to do the same in their 130 year span. Which kingdom(s) it is, is entirely up to you - though it should preferably be plausible (not like Habsburgs invade Russia and become tsars, sort of thing).
Have fun
The Luxemburgs are a similar story. Count Henri of Luxemburg, a ruler of a reasonably small state in the empire was elected as emperor in 1308. Emperor Sigmund of Luxemburg (his great-grandson) died in 1437, holding the titles of Holy Roman Emperor, king of Bohemia, king of Hungary and Croatia, and other members of his family had been margrave of Brandenburg (which he himself had also held) and of Moravia as well duke of Luxemburg.
The Habsburgs, on the other hand, had their first member elected in 1273 (Rudolf I), lost the imperial crown in 1308 (Albert I; although Friedrich the Fair held onto the German crown a bit longer (1330), got their next shot at the imperial dignity in 1437. This time proved more lasting, since with the exception of one reign in the 18th century, the Habsburgs (or Habsburg-Lorraines) ruled as emperors until the dissolution of the empire, amassing titles like king of Spain, Naples, Sicily, Sardinia, Hungary and Bohemia, duke of Burgundy, Milan, etc etc.
The Hohenstaufens and Luxemburgs burned bright for about a century before going extinct in the male line. The Habsburgs, however, managed to stick it out for the long haul. The challenge, should you accept, is simply this: pick a date - 1273 or 1437, and let the Habsburgs only last a few generations (both Hohenstaufens and Luxemburgs were on the throne for 130 years - interruptions aside in the latter case - so that would be 1403 for a 1273 date or 1567 for a 1437 date) on the imperial throne before going extinct. But there's a catch. Since both other dynasties (Hohenstaufen and Luxemburgs) held kingdoms outside the empire (Sicily-Jerusalem for the Staufers and Hungary-Croatia for the Luxemburgs), the Habsburgs need to do the same in their 130 year span. Which kingdom(s) it is, is entirely up to you - though it should preferably be plausible (not like Habsburgs invade Russia and become tsars, sort of thing).
Have fun