Toxin (real name is Wind Stream) is a pegasus who grew up wealthy with emotionally distant parents. Due to her cutie mark having nothing to do with flying as well as her lack of interest in flying, she was heavily bullied.  Wind is cold, misanthropic, nihilistic, and creepy.  Though despite all of that she does seem to find a sense of camaraderie with Silver Spirit and Midnight Meteor.  She studied botanical biochemistry, genetic mutation and psychology of fear.  By using her knowledge of toxins, poisons, phobias, and chemicals, she became the supervillain Toxin.  She's responsible for turning her friends into supervillains as well, forming a team known as the Terrible Trio.  Toxin acts the leader and the brains of the team.