Anyway, a plot hook to remove the Tsar from his capital involves going to war against this bunch of clownish marsh-dwelling folk.
For all the set-up and pomp, they are fairly easily defeated by putting the marsh grasses to the torch and some rather comical cannon-fire. In the end, hostages are freed and several of the marsh-men who didn't beat a hasty retreat are ended up captured...
(Pardon me if I don't have a correct name for these miscreants – They aren't named in the film, and my usual Google-fu prowess came up with limited info – so they are named for wild men of the marshes in Ukrainian lore....)
Lihiy Div (Marsh-man)
AC: 7 
Atk: 1 weapon (1d6+1)
Periodically erupting from the marshes at the edge of civilization, the Lihiy Div bands are stunted, primitive humanoids. Their appearance is almost a parody, appearing to be swathed in marsh grasses and furs, and almost headless, with bulging eyes, although this may be a mask worn to frighten foes and increase their own morale. Low-technological, they will tend to be armed primarily with bone and wood weapons. While Lihiy Div primarily raid farms and similarly poorly-defended areas for foodstuffs and livestock, they will occasionally kidnap people for unknown rites or sacrifice.
***Ok, so what if you want to run a PC as one of these illiterate, hide-and-grass wearing yahoos?
Advance/save as cleric.
You speak your own, guttural language, and may speak a max of two others at a competency of pidgin to simple conversational, with no written knowledge/literacy. And math is hard! You can count to ten.
You are proficient in the simple weapons of the hunter-gatherer: dagger (stone), club (wood or bone), spear (stone), staff, hand axe (stone), and sling. As a “primitive,” you eschew steel. However, you can craft exceptionally keen blades of stone/glass that cause +1 damage to unarmored/lightly armored opponents. You may create 1d6 of these per day, depending on available resources. The 'blade' may be a dagger, spear point, or axe blade.
Allowed armor includes hide (leather) armor, and perhaps a wood/rattan shield.
You maintain a healthy suspicion and fear of magical forces: +2 vs magic
You've eaten some weird shit and drank nasty water: +2 vs poison/disease
Lihiy Div with Wis >15 may be attuned with Nature and may cast druid spells at -1 level if desired. You may use a magic item usable by a druids. You may use potions, but must save vs. poison for them to be effective.
Option: Perhaps you don't want to be a simple mud-footed marsh-dweller. You can pick/roll a Favored Terrain to be a simple dweller from elsewhere... In your “home” terrain, you have only a 15% chance of becoming lost. You have a 3 in 6 chance to provide sustenance for yourself per day, and a 2 in 6 chance to provide sufficient victuals for a party. This increases by one per five levels. Pick/roll one, PCs with a WIS>15 may choose a second: