Complex sentence: He was also the chief magistrate and military commander of Transylvania's (seven) counties (except some administrative units eg free royal cities, Universitas Saxorum and Szekelyland), and this power inevitably drew the Székely and Saxon territories into his sphere of influence.
Split into simpler sentences: He was also the chief magistrate and military commander of Transylvania's seven counties, except for some of the administrative units-such as the free royal cities, Universitas Saxorum and Szekelyland. This power inevitably drew the Székely and Saxon territories into the voivode's sphere of influence.