Hunt Monsters. Save Humanity. Survive? Hidden Worlds Refined Core is a table-top roleplaying game set in the near future urban fantasy World of Incursion. The game runs on the HW20 Core System, which uses a single d20 for fast, deadly combat mechanics and a completely open magic system that is called "Faith." The Hidden Worlds Refined Core is a complete system overhaul of the original acclaimed release, Hidden Worlds: Incursion. This new version makes the combat system even smoother, makes the faith mechanics even easier to play, and enhances character creation. Hidden Worlds Refined Core is the definitive core manual for the HW20 Core System, and brought to you by Bryan Donihue, the One-Legged GM. No Classes. No Levels. No Limits. Welcome to the Hidden Worlds.