Source : Webster's Revised Unabridged Dictionary (1913)

Deviltry \Dev"il*try\, n.; pl. {Deviltries}.
   Diabolical conduct; malignant mischief; devilry. --C. Reade.

Source : WordNet®

deviltry
     n 1: wicked and cruel behavior [syn: {devilry}]
     2: reckless or malicious behavior that causes discomfort or
        annoyance in others [syn: {mischief}, {mischief-making}, {mischievousness},
         {devilry}, {devilment}, {rascality}, {roguery}, {roguishness},
         {shenanigan}]