Which adjective would describe a strange and mysterious occurrence?

The adjective "uncanny" effectively describes a strange and mysterious occurrence due to its connotation of something that is unsettlingly unnatural or extraordinary. When an event is labeled as uncanny, it implies an element of surprise or mystery that evokes a feeling of unease, often because it defies the expected or ordinary logic of reality.

In contrast, "simple" conveys ease or lack of complexity, making it unsuitable for describing something strange or mysterious. "Supercilious" refers to an attitude of superiority and disdain, which does not capture the essence of odd or bizarre occurrences. "Omniscient" describes a state of knowing everything, which does not relate to the strangeness or mystery of an event. Therefore, "uncanny" is the most appropriate choice for characterizing something that is both strange and mysterious.