Simple past tense and past participle of havoc.(verb)
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Use "havocked" in a sentence
"Many a shepherd at that time patrolled all night through with his dogs, only to find in the morning that the Killer had slipped him and havocked in some secluded portion of his beat."
"As never havocked scymitar made keenest at the curve."
"It havocked on his firm inflexible mind, as it would on a weak and pliant brain!"