The witch was everything you might expect: withered and aged, dressed in ragged black with a cowl to obscure her face, relentless, implacable.
I'm not sure why she was after me. (I might have known at some point during the dream, but I can't remember now.) But she stalked me through a park, then followed me into a grocery story - misting her way through a couple of locked doors to do it, which was pretty creepy.
What finally defeated her? She randomly attacked a shelf full of spices. Since there was something there she didn't like, we started opening up cnanisters and throwing stuff at her. The one that finally did it was something-bane. Wolfsbane? Monksbane? Ghostwitchbane? I dunno. Somethingbane, anyway. Good against spooky ghost-witches. Get your jar today, and keep it handy.
Perhaps more interesting than the earlier part of the dream (which was, after all, fairly typical being-chased-by-something nightmare material) was the next bit. Whatever the stuff was, it caused her to collapse in a puff of smoke. When she stood up, she wasn't anywhere near as old, or as... floaty? ...as she had been. And she wasn't hostile, though she was still a little odd-looking.
This, apparently, is what happens when I start trying to get enough sleep.