![Iron maiden](https://cdn.statically.io/img/static.wikia.nocookie.net/memoryalpha/images/a/a6/Iron_maiden.jpg/revision/latest/scale-to-width-down/180?cb=20090327214204&path-prefix=en)
A skeleton in an iron maiden
An iron maiden was a medieval Earth torture device that consisted of an iron frame in the form of a maiden – hence the name – that was enclosed around the victim who would locked inside and tortured.
After being locked-up in chains in an illusory castle on Pyris VII in 2267, Captain Kirk analyzed the various manifestations – dungeons, curses, skeletons, and iron maidens – observing that they were all Earth manifestations, leading Doctor McCoy to theorize that they were experiencing an Earth parallel development. (TOS: "Catspaw")