The Chromatic Chord is a series of books of two main kinds, and a bestiary beside them.

Foundations, this book (Parts I to V), holds what does not change from one era to the next. Part I, The Shape of the Cosmos, describes the planes behind the visible world, the places where they press into it, the edge beyond which nothing is, and the world’s own out-of-tune shadow, the Dissonance. Part II, The Powers, describes the ten impersonal forces whose currents run through everything, the powers people pray to, and what waits outside the ordered cosmos. Part III, The Laws of Magic, explains what magic draws on, what it costs, and how it is taught. Part IV, The Peoples of Caeldon, describes the peoples as kinds: their bodies, the shape of their lives, and the customs deep enough to survive every era. Part V, The Deep Past, tells the ages before any era of the series, the long threads that run through them, and the worlds that rose and fell before the present peoples built on their ruins.

The eras follow, each as a book of its own whose parts have the same shape. The first part of an era book shows the world in that era: who lives where, how a year runs, how people travel and what they meet at a border. The second describes the era’s peoples and powers: its civilizations, its faiths in practice, and magic as a village meets it. The third, and sometimes a fourth, is the era’s atlas, region by region. The last tells how the era’s present was made, and gathers the questions it leaves open. A reader who knows one era’s book will find the next one laid out the same way.

The first era book is The Medieval Era, around 1,350 CR. Its atlas has two parts, because its world has two halves: the forests, mountains, deeps, and river basins of the cradle-web, and the folds, scarps, coasts, and waters of the far side, joined by a single crossing. Later eras will join the series as books of their own, and the chapters already here will stay where they are. A Bestiary of Caeldon stands beside them, with the animals, plants, and other beings of the world. At the back of each book, a short chronology places the ages and eras its chapters mention on one line of time (this book carries the whole of it), a glossary explains in a sentence or two each name and term a reader may need to look up, and an index shows where each is told.

A reference into another book of the series names the chapter or section it points to and adds, in brackets, that book’s short form after the link: (FND). The short forms are:

Start where your story is.

A writer setting a tale in a particular region can open that region’s atlas chapter first and read outward from it: to the chapter on the region’s people, to the faith its villages keep, to the deep past that left the ruins on its hills. A writer whose story turns on a god, a spell, or a haunted valley can begin in Foundations and come forward to the era later. A writer who wants the whole of the present at once can read the first part of the era’s book, which is written as an overview, and then follow whatever catches.

Every chapter can be read alone, in a sitting. Each opens by saying what it is about, gives its essentials early, and tells its subject fully enough to be used without the others. Where a subject has its proper home elsewhere, a chapter gives as much as it needs and points onward rather than telling the same thing twice; the book tries to say each thing once, in the chapter where it belongs. The first time a chapter names a place, a people, an order, or an idea that matters to it, the name is set in bold, so a reader skimming for the thing they need can find it.

The voice of a chapter follows its subject. The cosmos and magic are explained as a natural philosopher would explain them, patiently and by their rules, because those rules are fixed and a story can lean its whole weight on them. The peoples are described as a traveller with an eye for customs describes them. The deep past is told as a history is told, in long spans and the few hard dates history keeps. The atlas reads like a guide and a gazetteer at once: the land first, then how people live on it, who holds power, and what they believe.

Around that voice, the world speaks for itself. Every chapter opens with an epigraph, and many quote further words inside the chapter, set apart from the text: a line from an almanac, a verse of a carters' song, an entry from a toll-roll, a passage from a treatise. Each of these comes from a named in-world source: a book, a chronicle, a song collection, a collection of sayings, given the name and the date it has in the world. These sources belong to this edition. They are voices, not records; they are not part of the world’s canon, and nothing in the setting depends on them. A source speaks as its people would speak, with their pride and their blind spots, and an almanac that calls a river cruel is telling you about the people who wrote it as much as about the river. The facts around these voices are not invented: those come from the world’s own pages.

Each era also has one traveller, whose road-book carries every traveller passage in that era’s atlas. For the Medieval Era it is Orrin Talloway, a Human toll-clerk of the Serathic League in the Lower Serath, who rode the roads of the cradle-web, crossed to the far side and back at the Glassbelt, and wrote both halves down around 1,350 CR in A Road-Book of Both Halves. Orrin writes with a clerk’s eye: for tolls and tallies, for who holds a road and what they take from it, for the small habits that tell a stranger where one lord’s word ends and the next begins, and for the tales told at every inn about what waits off the road. The road-book is arranged by region, as any road-book is, so each atlas chapter carries the passages for its own country, set apart in italic within the section of the place they cross. They can be read on their own, as a journey, or as part of the chapter around them.

In all of these voices, magic is shown rather than named. A carter’s song or a traveller’s road-book describes a working as an onlooker sees it: a cold blue light in a field, a word that stops a fall, a lie that turns the water dark. The names of spells and schools appear where people in the world would use them: in the explaining voice of the chapters, and in the mouths of scholars, teachers, and records.

Dates are counted in two directions from one fixed epoch. Years BR, Before Reckoning, count backwards from it into the deep past, so that 500 BR lies five hundred years before the epoch and 5,000 BR far earlier still. Years CR, Common Reckoning, count forward from it, so that 120 CR lies a hundred and twenty years after it. The Medieval Era stands at around 1,350 CR.

A date marked c., for circa, is an estimate, and nearly every date before the eras of this series carries one. The deep past is dated mostly in spans, plain windows of time such as c. 26,000-c. 16,000 BR, rather than in years anyone wrote down. A span says when something happened and how loosely that is known; it does not mean that the thing began or ended cleanly at either edge. Spans overlap where history did, and two peoples may live through the same thousand years quite differently.

The longest divisions of history are the ages, nine of them, which show where any event belongs and what else was happening at the same time. They are told in Part V. An era, such as the Medieval Era, is a stretch of history that the series describes in full, in a book of its own. Ages are how the world’s history is divided; eras are where the series stops and looks around.

Near the opening of most chapters stands a box headed At a Glance. It holds the chapter’s essentials, plainly and in a few lines: what the subject is, where it lies, who lives there or holds it, and when. It is meant for the moment in the middle of writing when one fact is needed quickly. The box summarizes; the chapter explains, and the reasons behind each line of the box are in the sections that follow it.

Each chapter closes with Tensions: the feuds, choices, dangers, and unsettled questions of its subject, the trouble a writer can pick up and carry into a story. They are written as facts of the world, the way a well-informed local would describe them, and not as advice. None of them has a settled outcome, and none is waiting for a particular kind of hero. A tension says that a bridge is failing and who blames whom. What happens next is not the book’s to say. The last chapter of each era gathers that era’s tensions by theme, for writers who want to see the whole field of trouble at once.