Woodsmen
Senior Militia
Older militiamen who have had some training and some experience on the battlefield. At the end of the day, they are still militia and won't hold up well against professional soldiers.
Novgorod Crossbowmen
A unique unit of Novgorod. Professional crossbowmen, protected with a large pavise-like shield.
Novgorod Home Guard
Gridni
Professional spearmen. Replaces the spearmen unit.
Druzhina
The personal soldiers of the Knyaz.
Druzhina will receive an extra armour upgrade to make them viable in the later stages of campaigns.
Chernye Klobuki
Steppe horsemen in the service of Kiev. Replaces the Heavy Horsearchers.
Brodniki
The forerunners of the Cossacks. Brodniki lived along the rivers in Rus territory. This unique unit for Kievan Rus has the advantage of being able to hide on the battlefield
Boyars
The Russian equivalent of feudal knights.
Heavy Boyar Cavalry
It's proximity to the west meant that Novgorod developed heavier cavalry than in other areas of medieval Russia. Novgorod's status as a major centre of trade meant that the armour of the richer Boyars is a mixture of Russian and western styles and technology.

Heavy Boyars also fight dismounted, where they forgo their shields and wield their blades with both hands.
Sulitsi Cavalry
Javelin throwing cavalry of Novgorod.

Cossacks
Swift and deadly, these masters of the steppe provide Kiev with great mobility on the battlefield.
Cossack Gunners
Streltsy
These musket armed militia are available to both Kievan Rus and Novgorod. Strictly speaking, Streltsy were only formed in Muscovy under Ivan Grozny. But given the fact that there is no Muscovy in SS and given the need for a late gunpowder unit for these factions, it's much better to have a unit that did historically exist, even if in a slightly different context. Oh and it should be pointed out that if Streltsy ever get into melee combat, their opponents will be in for a big (and historically accurate) surprise....
Russian Leaders
From left to right: Faction Leader, Heir, General and Captain