The Witch was never given a lot of depth in the original story. She's really just one of the many obstacles the Heroes have to overcome, and she's taken out pretty swiftly. I wanted to explore her more though, try and create a reason for why she is "wicked".
I know this has already happened in the Gregory Maguire book "Wicked". So why am I trying to write my own version? Because I can. I didn't really like Wicked a whole lot. It had some pretty interesting parts to it, but overall I felt like it wasn't something I cared for.
To get into the physical traits of the Witch, it's commonly known that water can melt her. So I incorporated that into my design for the Witch. If she can live for such a long time, surely she's cried. And so wouldn't tears actually burn her? I took this little idea and ran with it. In the original story the Witch only has one eye. Why? Well what if because her tears eventually killed that one eye, and the other has heavy black scarring around it.
Here's a video to help illustrate this design concept.