Earlier this month, a Cold War era chemical weapon developed by the Soviet Union was used in an attempted assassination in the UK of a former Russian Military Intelligence officer turned double agent for MI6. Sergei Skripal, the spy who was granted asylum to the UK in 2010, and his daughter Yulia, were found unconscious on a park bench in the quiet town of Salisbury, England. Within days, hundreds of military personnel, law enforcement officials, and emergency responders would descend upon the scene in protective HAZMAT gear, working tirelessly to decontaminate the area.

With such a dramatic and rapid response, one could be excused for assuming the UK government was being overly careful in the face of an unknown nerve agent – but when analysis of the agent at the scene came back, it was clear: an abundance of caution was not only wise, it was necessary. The culprit, it would seem, was “Novichok,” a nerve agent specially designed by the Soviet Union to defeat both physical, and even diplomatic, anti-chemical weapon defenses.

In fact, Novichok, which is translated from Russian to “Newcomer,” is so bad, even the men responsible for inventing it talk about it with a sense of fearful revelry; like Frankenstein, lamenting the monster he created.

“It’s real torture, it’s impossible to imagine. Even in low doses the pain can go on for weeks. You cannot imagine the horror, it’s so bad.” Vil Mirzayanov told UK media outlets earlier this week.

Prior to the fall of the Soviet Union, Mizayanov was a part of the team that helped to develop Novichok. He was so troubled by the chemical weapons he helped to create that Mizayanov, like Skripal, found himself betraying his country to do what he believed was right.

After it was discovered that Mizayanov was attempting to reveal the extent of the Soviet Union’s illegal chemical weapons manufacturing apparatus, he was charged with treason. He has since lived in exile in the United States.

VX has often been described as the deadliest of the common nerve agents found in use today, and recently made headlines in the North Korea-linked assassination of Kim Jong Nam in Malaysia last year. Novichok, which as far as the United States is aware, exists only inside Russian stockpiles left over from Soviet labs, is considered to be more deadly than even VX. Some experts contend that Novichok is slightly more potent than the legendary VX, while others argue that depending on dispersal method and potency, Novichok can be as much as five to ten times more powerful.

Novichok’s story begins in 1987, when Soviet scientists were tasked with producing a new, potent weaponized nerve agent with three very specific requirements. First among them, this new weapon needed to circumvent existing chemical weapons treaties by utilizing only components that had not been banned by international agreements. In doing so, the Soviet Union would technically have legal grounds to defend their use of the nerve agent, arguing that because Novichok itself wasn’t on the banned list, nor were any of its components, it technically would violate no treaty already in place.