Chwiliad am bobl sydd wedi cael eu labelu'n wrachod neu chwiliad am dystiolaeth o ddewiniaeth yw helfa ddewiniaid, neu helfa wrachod yn fwy modern yn y Gymraeg. Yng nghyfnod cynnar y Dwyrain Canol, roedd ymarfer swynion drwg neu swynganu wedi'i wahardd ac yn gosbadwy. Yn Ewrop ganoloesol, roedd helfeydd dewiniaid yn aml yn codi mewn cysylltiad â chyhuddiadau o heresi gan Gristnogaeth. Digwyddodd cyfnod dwys o helfeydd dewiniaid a ddigwyddodd yn Ewrop Fodern Gynnar ac i raddau llai yn America Drefedigaethol, o tua 1450 i 1750, gan gwmpasu cynnwrf y Gwrth-Ddiwygiad a Rhyfel y Deng Mlynedd ar Hugain, gan arwain at oddeutu 35,000 i 60,000 o ddienyddiadau. [1] Digwyddodd y dienyddiadau olaf o bobl a gafwyd yn euog fel gwrachod yn Ewrop yn y 18fed ganrif. Mewn rhanbarthau eraill, fel Affrica ac Asia, mae hela dewiniaid cyfoes wedi cael eu hadrodd o Affrica is-Sahara a Phapua Gini Newydd, ac mae deddfwriaeth swyddogol yn erbyn dewiniaeth i'w chael o hyd yn Sawdi Arabia, Camerŵn a De Affrica heddiw.
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