Question: What dissolved the privileges of the empire using Pan-Slavism as a political tool, the kingdom acquiring some Thuringian territory or Habsburg Monarchy?

Passages:
Some reordering of the Thuringian states occurred during the German Mediatisation from 1795 to 1814, and the territory was included within the Napoleonic Confederation of the Rhine organized in 1806. The 1815 Congress of Vienna confirmed these changes and the Thuringian states' inclusion in the German Confederation; the Kingdom of Prussia also acquired some Thuringian territory and administered it within the Province of Saxony. The Thuringian duchies which became part of the German Empire in 1871 during the Prussian-led unification of Germany were Saxe-Weimar-Eisenach, Saxe-Meiningen, Saxe-Altenburg, Saxe-Coburg-Gotha, Schwarzburg-Sondershausen, Schwarzburg-Rudolstadt and the two principalities of Reuss Elder Line and Reuss Younger Line. In 1920, after World War I, these small states merged into one state, called Thuringia; only Saxe-Coburg voted to join Bavaria instead. Weimar became the new capital of Thuringia. The coat of arms of this new state was simpler than they had been previously. Pan-Slavism, a movement which came into prominence in the mid-19th century, emphasized the common heritage and unity of all the Slavic peoples. The main focus was in the Balkans where the South Slavs had been ruled for centuries by other empires: the Byzantine Empire, Austria-Hungary, the Ottoman Empire, and Venice. The Russian Empire used Pan-Slavism as a political tool; as did the Soviet Union, which gained political-military influence and control over most Slavic-majority nations between 1945 and 1948 and retained a hegemonic role until the period 1989–1991. Poland's nobility were also more numerous than those of all other European countries, constituting some 10–12% of the total population of historic Polish–Lithuanian Commonwealth also some 10–12% among ethnic Poles on ethnic Polish lands (part of Commonwealth), but up to 25% of all Poles worldwide (szlachta could dispose more of resources to travels and/or conquering), while in some poorer regions (e.g., Mazowsze, the area centred on Warsaw) nearly 30%. However, according to  szlachta comprised around 8% of the total population in 1791 (up from 6.6% in the 16th century), and no more than 16% of the Roman Catholic (mostly ethnically Polish) population. It should be noted, though, that Polish szlachta usually incorporated most local nobility from the areas that were absorbed by Poland–Lithuania (Ruthenian boyars, Livonian nobles, etc.) By contrast, the nobilities of other European countries, except for Spain, amounted to a mere 1–3%, however the era of sovereign rules of Polish nobility ended earlier than in other countries (excluding France) yet in 1795 (see: Partitions of Poland), since then their legitimation and future fate depended on legislature and procedures of Russian Empire, Kingdom of Prussia or Habsburg Monarchy. Gradually their privileges were under further limitations to be completely dissolved by March Constitution of Poland in 1921.

Supporting sentences:
The 1815 Congress of Vienna confirmed these changes and the Thuringian states' inclusion in the German Confederation; the Kingdom of Prussia also acquired some Thuringian territory and administered it within the Province of Saxony. The Russian Empire used Pan-Slavism as a political tool; as did the Soviet Union, which gained political-military influence and control over most Slavic-majority nations between 1945 and 1948 and retained a hegemonic role until the period 1989–1991. Gradually their privileges were under further limitations to be completely dissolved by March Constitution of Poland in 1921.