Synonyms for Mischievousness (same or very similar meaning)
WordNet sense 1 (an attribute of mischievous children):
badness, naughtinessWordNet sense 2 (the trait of behaving like an imp):
impishness, puckishness, whimsicalityWordNet sense 3 (reckless or malicious behavior that causes discomfort or annoyance in others):
devilment, Devilry, deviltry, mischief, roguery, roguishness, shenanigan, mischief-making, rascalityFrom the ODE community, based on WordNetadd/edit