Moon of Israel by H. Rider Haggard

Bakenkhonsu was right. Save the son of Seti alone, none died who dwelt in or about his house, though elsewhere all the first-born of Egypt lay dead, and the first-born of the beasts also. When this came to be known throughout the land a rage seized the Egyptians against Merapi who, they remembered, had called down woe on Egypt after she had been forced to pray in the temple and, as they believed, to lift the darkness from Memphis.

Bakenkhonsu and I and others who loved her pointed out that her own child had died with the rest. To this it was answered, and here I thought I saw the fingers of Userti and of Ki, that it was nothing, since witches did not love children. Moreover, they said she could have as many as she liked and when she liked, making them to look like children out of clay figures and to grow up into evil spirits to torment the land. Lastly, people swore that she had been heard to say that, although to do it she must kill her own lord's son, she would not on that account forego her vengeance on the Egyptians, who once had treated her as a slave and murdered her father. Further, the Israelites themselves, or some of them, mayhap Laban among them, were reported to have told the Egyptians that it was the sorceress who had bewitched Prince Seti who brought such great troubles on them.