Sympathetic magic was a concept from Human mythology. It involved the manipulation of symbol or representation of things to affect them. For example, a picture or doll that looked like a person was similar to, and hence sympathetic with, the actual person might be believed to affect that person.
In 2267, the USS Enterprise encountered extra-galactic explorers Sylvia and Korob. They likened their science to sympathetic magic on several occasions. To murder Crewman Jackson, Sylvia constructed an image of him, and in her thoughts that image was Jackson. When she killed it, and knew that it was dead, the real Jackson died. Later, she passed a small replica of the Enterprise through a candle flame, and this caused the real ship to experience dangerous levels of heat. To prevent the Enterprise from sending a rescue party, Korob then encased the model in a clear crystal, creating an "impenetrable force field" around the ship. (In fact, the field was not impenetrable; DeSalle and Chekov discovered an electrical field that weakened and would eventually have destroyed Korob's field.) (TOS: "Catspaw")
Background information Edit
Futurist and science-fiction author Arthur C. Clarke famously stated that any sufficiently advanced science was indistinguishable from magic. Whether the science employed by Sylvia and Korob was very advanced, or merely different, is debatable.
A typical candle burns at around 400 °F (205 °C), which is far lower than temperatures the Enterprise hull experienced on other occasions. It is therefore reasonable to conclude that the technique employed by Sylvia magnified the heat experienced by the model or that the heat was not produced by the actual ritual.