Mercury



Mercury is a metallic, chemical element that will result in death after prolonged exposure. It was used on Avatar Korra in 171 AG in an attempt to end the Avatar Cycle for good; as a natural reaction, she would enter the Avatar State to fight off the poison, which would enable the Red Lotus to kill her in the state.

History
In an attempt to bring forth worldwide anarchy, the Red Lotus intended to permanently end the Avatar Cycle. Having captured Avatar Korra, they administered the poison, which immediately produced a physical and mental reaction. As a side-effect, the poison caused Korra to hallucinate, seeing the Red Lotus members' faces turn into those of Amon, Unalaq, and Vaatu. Although she attempted to resist the poison's effects, she eventually caved in and she was forced into the Avatar State. Before she could be killed, however, the surge of power she received from Raava's spirit enabled her to break free from her chains and fight off her captors. She subsequently locked into battle with Zaheer, though Korra found herself struggling to fight both him and the poison coursing through her veins, which gave Zaheer the upper hand. With the help of the new airbenders, she was able to overcome him, but she succumbed to the poison nonetheless, her body having been exposed to the lethal substance too long. Jinora spurred Suyin to action, however, when the young airbender revealed that the venom was metal-based and Lin's younger sister promptly removed most of it from Korra's system, saving the Avatar's life. Nonetheless, the poison had caused significant internal damage, rendering Korra unable to walk for nearly six months and incapable of contacting Raava or entering the Avatar State. In addition, some traces of the substance remained in the Avatar's body, weakening her.

Effects


The metallic poison is administered to the body by metalbending it into the victim's pores. Once administered, it has a hallucinogenic effect. After that stage, the victim will be slowly but surely hindered in their movements until the strain on their body eventually becomes too painful to bear and they will slip into unconsciousness, eventually resulting in death.

When used on an Avatar, the Avatar State will naturally react to the lethal threat and be activated in an attempt to fight it off.