The Witch Transmigrates to Take Down Her Love Rival and Become Empress

A witch transmigrates into the body of the Marquess of Xining’s wife, only to discover that her husband has been secretly having children with her half-sister and making the original owner raise them. The witch takes on her husband’s mistress, casually turns the cheating pair against each other, then builds up her own power, conquers a small kingdom, and crowns herself empress.