sphinx-like

See: mysterious
References in classic literature ?
Franz did not doubt that these plans were the same concerning which the count had dropped a few words in the grotto of Monte Cristo, and while the Count was speaking the young man watched him closely, hoping to read something of his purpose in his face, but his countenance was inscrutable especially when, as in the present case, it was veiled in a sphinx-like smile.
Wingrave was standing upon the hearthrug, cold, passionless, Sphinx-like.
He turned on his moccasined heel and walked out, imperturbable, sphinx-like, neither giving nor receiving greetings nor looking to right or left.
They were Chinese, with expressionless, Sphinx-like faces, and they walked in peculiar shambling fashion, dragging their feet as if the clumsy brogans were too heavy for their lean shanks.
He never speaks to her; he is at all times a man of few words, but, as far as Minora is concerned, he might have no tongue at all, and sits sphinx-like and impenetrable while she takes us to task about some remark of a profane nature that we may have addressed to him.
An example of her appeal is the segment titled "Personal Expert," which contains 150 sphinx-like queries that reveal the utter absurdity of most of any reader's basic life assumptions.
Kolchin owes his notion of a sphinx-like South to the late David Potter, whose comparative work--often pursued at the international level--he groups with that of C.
On the Star Wars absurdity ($55 billion and counting), Bradley has maintained a sphinx-like silence.