Former Undead Transmigrated to become Villainess's Butler

Bored of his monotonous life, one undead discovered transmigration magic, and hopped across various worlds until he stumbled on the human realm and lived up to the twenty first century. His dissatisfaction with the role of villainess in the Otome games forced him to take a drastic step and transmigrate into another world of kingdoms and empires, and perhaps the unnatural harem of the heroine. Nurturing the pitiful villainess into a formidable villainess in his goal, and he decides to achieve it without magic. But everything proves to be challenging when he discovers insane magicians in the world, and ravaging monsters that might force him to remove his self-imposed handicap. Note: This is not a redemption story, so don't expect the villainess to redeem herself. All characters (main) are morally twisted.