Idolishche Poganoye (Russian: Идолище Поганое) is a mythological monstrosity from Russian bylinas (epic tales) which personified pagan forces invading the Russian lands. The name literally means "pagan idol", with a Russian augmentative suffix "-ishche".
The major epic sources that involve Idolische are various variants of the bylina "Ilya Muromets and Idolishche Poganoye" ("Илья Муромец и Идолище Поганое"), where Idolishche is also characterized as "Tatarin", in reference to the Tatar-Mongol yoke.
References
Idolishche Wikipedia(Text) CC BY-SA