In Nobilis, players are former mortals who have been raised to immortality ("Ennobled") by being given a piece of creation's power by an Imperator, one of the otherworldly beings of The World Ash - the game setting's depiction of the cosmos. Each Noble is given sovereign power over an aspect of reality - War, Music, Noble Gases, Carnivorous Plants - whatever the player can imagine. They and other members of their Chancel take part in the conflict with The Excrucians, beautiful beings from beyond the World Ash who seek to destroy Reality.

The game is diceless and actions are resolved by the use of Ranks of 0 - 10 based on Attributes and aided by Miracle Points. Players create their characters' powers in line with their concept of the character's Incarnation. Players also, in cooperation with the Hollyhock God (i.e., the GM), create their characters' Imperator (the Power who ennobled them) and their Chancel (the otherworldly space from which the PC's operate).

Snippets of strikingly imaginative and well written microfiction are scattered generously through the text as sidebars, effectively setting the tone of the game.