adjective. Of, relating to, or being a religious mystery.

adjective. Arousing wonder or curiosity, especially by being difficult to explain or understand.

Partaking of or containing mystery; obscure; not revealed or explained; unintelligible.

Expressing, intimating, or implying a mystery: as, a mysterious look; his manner was very mysterious and important.

adjective. Of or pertaining to mystery; containing a mystery; difficult or impossible to understand; inexplicable; obscure; not revealed or explained; enigmatical; incomprehensible.

adjective. Of unknown origin

adjective. Having unknown qualities

adjective. having an import not apparent to the senses nor obvious to the intelligence; beyond ordinary understanding

adjective. of an obscure nature

"I must frankly admit, however, that, either owing to the derangement of my nerves, or my new impressions in my new lodgings, or my recent melancholy, I gradually began at dusk to sink into that condition which is so common with me now at night in my illness, and which I call mysterious horror."

esoteric  incomprehensible  inexplicable  

mystery  

mysteriously  mysteriousness  

deleterious  delirious  imperious  serious  

magical  new  terrible  wonderful  

able  abstruse  ambiguous  amphibological  amphibolous