Poludnitsa

A Poludnitsa, sometimes called "Lady Midday", is a cruel fey who appears as a young, beautiful woman dressed in white and holding a scythe. She enjoys engaging in conversation, asking complicated and difficult riddles. If one answers correctly, she might tell them a great secret (spoken in riddles, of course). If a wrong answer is given, however, she will cause the one answering to suffer a heat stroke; the victim must save vs. Spells or take a -4 penalty to all attack rolls and ability checks for the next 2d6 hours.

A poludnitsa is usually mischievous rather than outright evil, but if threatened she will attempt to behead her foes with her scythe.