Perun
since we are talking about evil vs good and a Biblical battle. I believe these evil entities are still very much alive, thanks to the elites constant worship through the ages.
Info on Perun
Of all historic records describing Slavic gods, those mentioning Perun are the most numerous. As early as the 6th century, he was mentioned in De Bello Gothico, a historical source written by the Eastern Roman historian Procopius. A short note describing beliefs of a certain South Slavic tribe states they acknowledge that one god, creator of lightning, is the only lord of all: to him do they sacrifice an ox and all sacrificial animals. While the name of the god is not mentioned here explicitly, 20th century research has established beyond doubt that the god of thunder and lightning in Slavic mythology is Perun. To this day the word perun in a number of Slavic languages means "thunder," or "lightning bolt".
The Primary Chronicle relates that in the year 6415 (907 AD) prince Oleg (Scandin.: Olaf) made a peace treaty with the Byzantine Empire and by taking his men to the shrines and swearing by their weapons and by their god Perun, and by Volos, the god of cattle, they confirmed the treaty. We find the same form of confirmation of a peace treaty by prince Igor in 945. In 980, when prince Vladimir the Great came to the throne of Kiev, he erected statues of five pagan gods in front of his palace which he soon thereafter discarded after his Christianization in 988. Perun was chief among these, represented with a silver head and a golden moustache.
May be crazy but who knows for sure. Don't hate my input