Sentence:  The terrible spectacle drove for the instant all thought of rebellion from my mind. My very blood froze in my veins and I stood motionless. I heard Hassim laugh grimly behind me. The eyes in the cadaverous face blazed <WSD>fiendishly</WSD> at me and I blanched from the concentrated satanic fury in them. 
Meaning of the word marked with <WSD> tags:  In a fiendish manner; evilly, wickedly.