The word mare is Old English for "demon." In olden days, people believed that troubled sleep was caused by a demon who rode you like a horse while you slept. The terrible things you dreamt were the experiences from the ride. To protect yourself from nightmares and interrupted sleep, find a sacred holey stone. Thread a string through the hole and hang it by your bed. Repeat this old German charm:

I lay me here
to sleep;
No nightmare shall plague me;
Until they swim all the waters;
That flow upon the earth;
And count all the stars; That appear in the
firmament!
As I will, so mote it be.