mystic has 6 distinct synonyms spread across 4 of its 4 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
having an import not apparent to the senses nor obvious to the intelligence; beyond ordinary understanding
“mysterious symbols”
relating to or characteristic of mysticism
Synonyms, antonyms and the broader and narrower relations for mystic come from Princeton University’s WordNet. Full sources and licences.
“mystical religion”
someone who believes in the existence of realities beyond human comprehension