The story so far:

After rescuing Tamara last season, and then rescuing Alixandre from Fleur and Marceau, Tamara asked you all to join her in Pavtlow, hoping that you could help negotiate peace between Ussura and Montaigne. After several days of traveling (and some encounters with bug-like creatures and some 'Snow Maidens'), you made it to Pavtlow, and from there to meet Montegue, where you revealed that 'Devoe', his advisor was actually another bug creature. You convinced him to enter the same egg you all had traveled to the past in, and when he returned, he agreed to negotiate for peace.

During the peace talks, however, everything blew up. A strange spell threatened to destroy the Gaius's spirit skins (as well as those of the other Kniases who were still there), and the Gaius himself was killed. This in turn turned out to be part of a larger plot on the part of Wolf and the Knias Alexsi to destroy Matushka--when she merged with the land to choose the next Gaius, Wolf attacked. You haven't seen her since. Wolves loyal to Wolf attacked Pavtlow, but you all managed to escape to a refugee camp a bit outside the city with the Gaius's wife Ketheryna, who turned out to have been granted Pyeryem. Tamara went back to her province (Gallenia), and Ketheryna hopes to make it to Somojez to rally the people behind her and guard against any moves by Alexsi. The safest place seems to be with Montegue's army, so that's where you've been headed.

And Montegue needs you--none of his supply mages have returned with supplies recently, and he fears L'Empereur may be behind it. Having you all with him, he hopes to negotiate with the locals for supplies (as had been agreed in the aborted treaty), which should sustain the army long enough to be able to make it to the coast, where he can make better time back to Montaigne in the fleet.

The strange encounters haunting Pyotr turned out to be the drachen spirit skin of the Knias Pyotr had accidentally killed years ago in a bar fight. (Valerii, the man forced by the oprechnika to take Borin's place, is done playing Knias, and would like nothing better than to go back to being a merchant again.) The drachen said he would agree to be bound to your choice for a new Knias of Somojez... if you agreed to wake his counterpart, the drachen that sleeps under the castle at St. Adrevgorod.