Through the Breach uses cards instead of dice to resolve the actions of the Fated and those around them. The basic rules are simple: flip a card from the deck, add the character's Skill rank and Aspect modifier, and compare it to the total of the opponent. The highest total wins the conflict, with increasingly greater margins of success leading to greater magnitudes of victory.

The player characters - or Fated, as they are called - each belong to a Pursuit, which functions as a combination of class and profession. Pursuits are fluid, with the characters choosing which Pursuit they wish to follow at the start of each session, after a short prologue. This allows the Fated to prepare themselves for the adventure to come; sessions with lots of combat will result in Fated who have chosen more martial Pursuits, while investigative or social adventures will find the Fated well-matched to uncovering the correct clues or charming the right people.

At the end of each session, the Fated character gains an ability based upon the Pursuit they played on that adventure. This allows characters to grow organically in multiple directions, as a product of their adventures. For instance, take a look at Pedro Ortega, who primarily adventures as a Gunslinger, save for a few sessions where he decided he could do more good as a Performer. He's still a quick shot and deadly with his pistols, but his dazzling smile and friendly demeanor easily smooth over those delicate social situations that can't be solved by just shooting someone.

Each Fated character possesses a destiny, which give the Fatemaster vague, cryptic phrases that can be used to build an entire adventure. In this way, each session's focus tends to focus on a single character as they resolve a step of their destiny with the help of their friends and allies. As the Fated travel together, their destinies weave together into a communal story, shifting its focus back and forth in the manner of an television show featuring an ensemble cast.

Whenever a Fated character resolves a step of their destiny, their strengthening destiny begins to manifest itself in various effects. For some characters, this results in an increase to their physical or mental abilities, pushing them well beyond the capabilities of normal humans and into the realm of the truly exceptional. Other characters develop Manifested Powers, unique magical abilities that the player can tailor specifically to match their character and the events surrounding their Fated's destiny. Spectral bullets that pass through walls, a voice that puts others to sleep, the ability to animate the dead with a single touch... the only limit is the player's imagination (and the sanity of the Fatemaster).