Something wicked this way comes

Double, double toil and trouble;
    Fire burn, and caldron bubble. 

This is of course from the Scottish Play, first acts, an incantation of the three witches. But it could also fit Halloween easily: witches, witchcraft, etc. And it was turned into a song in one of the Harry Potter movies (this one if I am not mistaken), sang in an Halloween scene. I usually upload a song for Halloween, this one is perfect. I do not have three witches, but I do have three Jack O'Lanterns, an Unholy Trinity. So here it is.