Witches of East End outdoes itself again with “Potentia Noctis,” an episode so chock full of sex, intrigue, and magic, it leaves some lives fair game for ultimate disaster. “Potentia Noctis” is not only a game changer, putting all the pieces of the puzzle together about the elusive shape-shifter, but it sheds light on the cause for Joanna (Julia Ormond) and Wendy’s (Mädchen Amick) 100-year estrangement.