Iron Heroes is a set of variant rules for the d20 System, written primarily by Mike Mearls and originally published by Monte Cook's Malhavoc Press. It is a complete game, and does not require the Dungeons and Dragons rulebooks.
The game was originally announced as "Iron Lore", but this was contested by Iron Lore Entertainment, developers of the computer roleplaying game Titan Quest. The title was changed before release.
Ownership was transferred by Cooke on March 1, 2007 to Adam Windsor, a freelance writer who worked extensively on the official errata for Iron Heroes almost since the product's release. Further titles in the line are being published by [Fiery Dragon Productions]. In addition, other companies have published third-party adventures and other OGL material for Iron Heroes.
Iron Heroes redesigns or expands many of core features of the d20 system, especially the combat, feat, skill and magic rules, to suit generally low-magic campaigns focussed on action and combat. It is designed to be independent of any particular campaign setting, instead geared towards serving a gritty, darker genre of fantasy, and Dungeon Masters are encouraged to develop their own settings for use with the game. These two main features are in sharp contrast to Cooke's own Arcana Unearthed and Arcana Evolved, which comprised a developed high-magic campaign setting with rules which expanded magic use and power in that setting.
Iron Heroes characters do not acquire magical equipment or supernatural abilities as they gain levels, as is normal for most characters in Dungeons and Dragons style fantasy campaigns. Instead they train in various combat styles and ability trees, granting them numerous skills and combat options. Most classes gain access to a pool of tokens that may be spent to perform extraordinary feats. These tokens represent an inner resource (e.g. bloodlust, focus or superior knowledge) or advantageous circumstance (usually created by the character; e.g. spending time aiming at a foe before firing, or deceiving an opponent with feints).
Magic is generally perceived as evil, corrupting and dangerous; only one heroic class is able to make use of it, though various forms of magic are available to some of the villain classes introduced in Mastering Iron Heroes.