Upior
The Upior is a form of vampire from Polish myth and was a common belief among the Ruthenian people. This term is a reinterpretation of the Russian Upyr into Polish myth in the seventeenth century. They are sometimes believed to be dead people possessed by the devil often described as swollen blood-filled corpses. This blood-filled appearance led to the phrase “red as an Upior” becoming popular. Someone born with two hearts, who later grows evil was thought to become an Upior. Corpses suspected to be at risk of rising would be staked in the heart, burned, decapitated and staked, or have pig manure stuffed in their mouths. It was also believed that if an Upior was buried on their stomach, and their hands were bound behind them, then they could only act during a full moon. An Upior grave could be found by having a young boy ride on a virgin stallion, the horse would react violently when led over the Upior grave. When they rose, they would devour their burial shroud and bring disease to both men and cattle. In some areas, the Upior would hunt until the first crow of the rooster but did not drink blood. Some believe these beliefs were exploited so the clergy could charge for more exorcisms. There was a case in 1783 where a woman who had killed someone, and claimed an Upior was responsible.
Citations:
Bohn, Thomas M.. The Vampire: Origins of a European Myth. Germany, Berghahn Books, 2019.