skein, skene

Skein or skein means a length of yarn or thread, wound around a spool or reel, or something that is wound around in circles in this way--
I thought I had another skein of yarn; I'll have to make this a vest instead of a sweater.
The kitten got a skein of yarn out of the basket, and made a mess of it.

Skene or skene means the structure that forms the backdrop for players on a stage--
The skene should be painted with a temple and some trees.
We left the skene a blank wall; the audience will have to imagine the setting.

Now that you know that, you can say--
"When the witch unravels the skein of yarn, the skene should be moved forward a bit, making the stage smaller as the yarn runs out."

Note--"skean" means a knife or dagger once used in Scotland or Ireland--
He wore a kilt, with a skean tucked in his sock.