In Brian Boru: High King of Ireland, players strive to unite Ireland under their domain, securing control through cunning, might, and matrimony. Build monasteries to extend your influence, join forces to fend off Viking invaders, and gather support in towns and villages throughout the land. To become High King of all Ireland, you will need to navigate a web of shifting alliances, outmaneuver your enemies, and grab history by the reins.

The success of the historical Brian Boru rested on three pillars: favor he managed to garner with the Church, his victories against the Vikings, the and the alliances he forged through political marriages. This became the foundation of this game, with each pillar becoming a suit in the trick-taking that forms the core of the gameplay mechanisms. Win a trick and you gain influence in a town, which, in turn, gains you majorities in the different regions; if you lose the trick, however (deliberately or otherwise), you instead take an action corresponding to the suit of that particular card.