Giulia Tofana may have been one of the deadliest "serial killers" to ever live.

The Italian woman is believed to have aided in the murder of nearly 600 men during the 17th century. Despite the body count, Tofana has been hailed a hero by the women she helped escape toxic relationships.

Women living in abusive marriages during the 17th century had no rights and no options for escape until their husbands passed away.

Tofana's criminal mastery wasn't in heinous slayings. Instead, the assassin helped women take matters into their own hands by selling them poisonous potions under the guise of cosmetics, including makeup, lotions and perfumes.

For nearly 20 years, Tofana crafted and sold bottles of her lethal concoction, which included an undetectable arsenic.

The potion would allegedly give victims cold-like symptoms before perishing within a few days. Plus, the colorless, odorless poison was untraceable, allowing many wives who were stuck in abusive relationships and women who wanted to flee sex trafficking to escape scot-free.

Tofana's branding included a simple logo depicting Saint Nicholas —  the patron saint of children and unmarried people. Her business spread via word of mouth, with the product dubbed Aqua Tofana.

According to historian Mike Dash, Aqua Tofana offered a "severe challenge" to "a world in which men ruled as petty tyrants over their own families."

Tofana was eventually exposed by a client who panicked and confessed to her husband while serving him poisoned soup.

According to Dash, it's possible Tofana escaped criminal prosecution by seeking sanctuary at a church while continuing to make her poison. Others believe she was captured, tortured and arrested.

Historical records are unclear.

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