The gnarly nailed hands belong to Agatha Harkness. At this time, she (the Fantastic Four’s nanny and one of the original witches from the Salem Witch Trials) was teaching Wanda how to control her mutant “magic” powers. See, originally Wanda’s power was described as changing reality/probability. Here, we learn that this ability is at least similar to magic in how it is controlled and manifested by the user. So, finally, she actually was becoming a witch.
I posted this picture just because it’s creepy.