[The Colonel]

As a monster, you are probably looking at both the Crone archetype, and the Hag - which are often conflated as both being similar in appearance to ugly old women ... of course, the hag is an anthrophagous monster (viz. Jenny Greenteeth, Black Annis), possibly with fae connections, that just happens to look human rather than a transformed human. Unless, of course, you decide that that's precisely where hags come from: evil female magicians that have sacrificed a lot of their humanity to become an immortal monster.

And then we get Baba Yaga knock-offs. And Baba Yaga is another scale of entity altogether - possibly the relic of a pagan deity, as much as a witch or hag.