Avatar Vanquishing Potion

The Avatar Vanquishing Potion was originally created by the ancient civilization of Egypt. It was created to vanquish individual Avatars and weaken the collective. The potion was kept in tightly sealed ancient Egyptian vials, and the only way to release the contents is to break the containers in question.

Ancient Egypt
It was believed that this potion was created by the mage Anubis when the Avatars tried to create Utopia in the time of Ancient Egypt. The threat of this potion was so great that the Avatars had to retreat, with the intent of returning to once again instigate Utopia when the world is ready to accept it.

2004
Kyle Brody tried to use the potion three times, two failed attempts to kill Leo Wyatt and a successful attempt to kill Beta.

After Utopia had commenced, Zankou retreated to Egypt, where the ancient protections there prevented the place from being monitored even by the Avatars. From there, he studied the archaic drawings depicting how the potion was made, hoping he could recreate it.

However, he realized that he could not without assistance from the Charmed Ones. When the sisters turned on the Avatars, Zankou convinced them to brew a new batch based on what he learned from the drawings. They later confronted the Avatars, threatening to vanquish them then and there, unless they undo Utopia.

2036
After becoming an Avatar, the half-demon Jared asks Avatar Delta if he can still have a life in the Underworld and be an Avatar. Delta explains that the only purpose of the Avatars were to create Utopia. Jared tells Delta there some things he had to change first. Delta doesn't understand and Jared calls out for his sister, Jessica. Jared tells Delta he has to leave, for which he fades out. Jessica reveals the Avatar Vanquishing Potion and explains to Delta that she had found the formula to concoct the potion. Jessica then throws the potion at Delta's feet and the gray smoke from the potion kills Delta.

Not long after Jared changes the world to his liking, Avatar Sigma visits Jared and explains that she was sent to ask him to undo the change. Jared asks Sigma what she is going to do to him and goes on to tell her that he knows how to make the Avatar Vanquishing Potion. He also says that his sister is the only person who knows where he keeps extra vials of the potion for just in case.

Effects of the Potion
When a potion bottle breaks, it releases grey smoke, which seeks out and enters the Avatar through both the mouth and nostrils. The smoke acts as a poison that will kill them almost instantly.