But by far the larger number of his stories, which, be it observed, are warranted as ordinary occurrences, as to the possibility of which there was no question, are coloured by that more sinister side of supernaturalism so much emphasised by the new theology.
The mediaeval devil was, for the most part, himself little more than a prankish Ruebezahl, or Robin Goodfellow; the new Satan of the Reformers was, in very deed, an arch-fiend, the enemy of the human race, with whom no truce or parley might be held.

The old folklore belief in _incubi_ and _succubi_ as the parents of changelings is brought into connection with the theory of direct diabolic begettal.
Thus Luther relates how Friedrich, the Elector of Saxony, told him of a noble family that had sprung from a _succubus_: "Just," says he, "as the Melusina at Luxembourg was also such a _succubus_, or devil." In the case referred to, the _succubus_ assumed the shape of the man's dead wife, and lived with him and bore him children, until, one day, he swore at her, when she vanished, leaving only her clothes behind.
After giving it as his opinion that all such beings and their offspring are wiles of the devil, he proceeds: "It is truly a grievous thing that the devil can so plague men that he begetteth children in their likeness.

It is even so with the nixies in the water, that lure a man therein, in the shape of wife or maid, with whom he doth dally and begetteth offspring of them." The change whereby the beings of the old naive folklore are transformed into the devil or his agents is significant of that darker side of the new theology, which was destined to issue in those horrors of the witchcraft-mania that reached their height at the beginning of the following century.
One more story of a "changeling" before we leave the subject.

Luther gives us the following as having come to his knowledge near Halberstadt, in Saxony.

A peasant had a baby, who sucked out its mother and five nurses, besides eating a great deal.