Avenger Eston is the creation of Samantha Flynn (Booksbooks3). You can read more about them here.
Avenger Eston, previously known as Glove Drop during their time in the Black Gloves, is an alchemist and infiltrator for the Cyran Avengers. She spent much of her teenage years working as a bartender in the city of Eston, making all kinds of (magical or otherwise) drinks and concoctions that ultimately drew the attention of Glove Spectre.
Her most impressive achievement was getting a poison past House Medani security to kill an Aundairian war criminal.