Marco Leon is the designer of the Jacob's Ladder and World Turtle systems. He is also the designer of Enter the Shadowside, which utilizes both.
Marco Leon founded FableForge to publish this game and future supplements.
In 1996 Marco created a homebrew game called "Fantasya", which he played with close friends until 2000, when he left Morelia, Mexico, for New York City. The core rules from Fantasya -namely the 14 Traits and basic Might vs. Difficulty resolution- were imported into an online version of Fantasya Marco had created in 1999, called Vaxia. He created the Jacob's Ladder for Vaxia in order to have a system with no automatic wins nor failures, scalable to any kind of dice and any number of points, and requiring no mathematical operations to be performed. A Vaxia player, Steffen, was able to convert the ladder into a mathematical formula which Vaxia's server-side-scripts could use.
Marco left Vaxia in 2006, serving as a screenwriter and script doctor for various film projects until 2008, when he devoted himself to the Shadowside project as an evolution of "Grittie", a 2005 40-issue comic book Marco had written and illustrated which introduced the concepts of "Hierogamy", the "Shadowside", and various shadowside organizations including "Fujin's Blood", "Greater Thelema Society", and others. Inspired by /x/'s creepypasta, the project was originally meant to be about as a single group, SCaV3NG3R, and conceived as a series of point-and-click web games (for which Marco programmed an online engine), short films, comic books, novels, and a feature length movie. Development was paused during 2010 for the writing of "Los Bandidos de Artaban", an animated post-apocalyptic film currently being produced in Mexico.
In 2011, the project morphed into an RPG utilizing Fantasya's World Turtle, Vaxia's Jacob's Ladder, Grittie's setting, and SCaV3NG3R's organizations. The project received help from many creative supporters in /tg/ and /r/rpg, being finally released in April 2012.