[7] In 2018, Rob Heinsoo Games and Chaosium published an alternate setting supplement for Greg Stafford's Glorantha.

[8] 13th Age was designed to be familiar in terms of setting concepts to D&D players, so it is a class-based game with the main rulebook containing standard D&D classes.

Players are encouraged to create backstories for their characters that give them bonuses to actions in the game, often asking them to refer to a time in their fictional past when they have dealt with a similar obstacle and how they overcame it or what they learned from the experience.

Other differences from standard d20 games include the backgrounds taking the place of most utility magic, weapon damage dice being determined by class, spells that are only expended on bad rolls, and recoveries that resemble D&D 4e healing surges.

[12][13] In December 2022, the 13th Age SRD was updated to version 3.0 to add classes, monsters and multi-classing rules from the 13 True Ways and Bestiary supplemental books.