Slavania

Let's embark on an alternative Rus. In a place of feudal fragmentation, raids by the Polovtsians, and Vladimir Monomakh, we will have a mermaid on the branches, a wise cat, and withering gold... or rather, the Tsar Koshchei, ruler of the underworld.

Slavaina is an indie platformer, or more precisely, a metroidvania from Russian developers (who else?). The action takes place in Ancient Rus during the 11th-12th centuries.