She is best known for her work on various television series including Jem,[1] Teenage Mutant Ninja Turtles, Conan the Adventurer, G.I.

She is also known for her comic book work, including her original comic book series Sisterhood of Steel as well as work on Conan, Red Sonja, and Elfquest.

Marx's earliest published works in the comics industry included Red Sonja stories.

[8] In June 2012, it was announced that Marx would be writing the character of Amethyst, Princess of Gemworld in a revival of the comic book series Sword of Sorcery, which was released in August 2013.

The computer game Conquests of Camelot[12] and the Sisterhood of Steel graphic novel features his art.