Tsar Rising is an adventure for 8th- to 9th-level characters. From the back cover:

The Tsar is Dead!

The cry echoes across Torassia: the cruel tyrant fell in a battle with undead troops, abandoned by the two princes in his time of need. The empty throne creates anarchy and chaos, as the princes and the Tsar's advisor battle for the right to rule. As if that wasn't bad enough, the worst winter that Torassia has ever experienced leaves frozen corpses in villages everywhere. It's a race against time as Sergei, the Tsar's commander in chief, gallops southwards to reach the capital before the forces of hell get there first.

Will you brave the coming storm?