Preface

The Advanced Dungeons & Dragons 1st Edition Player’s Handbook (PHB) has a narrow brief: here are the races, here are the classes, here is how your character is built and described. It delivers that brief efficiently, and most of it holds up. Most of it also applies in Oath-Bound as written, which is worth saying plainly before anything else.

If you are a player who has read the PHB and is coming to Oath-Bound for the first time, the majority of what you already know will serve you. Your character is built broadly the same way, the domains are recognizable, and the attributes mean what they mean. The differences are real but they are not wholesale.

Oath-Bound — an AD&D 1e Evolution — is the rules system used in Under Oath: The Far Reaches, a campaign set in Caldris: a mythic world where promises have real and not metaphorical power. In Caldris, a sworn oath is noticed by the gods, carries consequences beyond reputation, and underpins the social and legal order in ways that shape everything a character does. That premise is the engine of the system and the world it runs in.

Oath-Bound is organized around oaths — binding promises with real weight, sanctioned by gods who enforce the consequences of breach. The social and legal structure of the setting runs on sworn obligation, so characters with social standing, institutional affiliation, or anything to lose operate in an environment where what you swear matters. Players who engage with that seriously will find it produces a different quality of play than the dungeon-clearing model the PHB was designed for. Players who ignore it will find the world ignores them back, not punitively but thoroughly.

What this website does — the Advanced Dungeons & Dragons 1st Edition Player’s Handbook Overlay (PHBO) — is take the PHB section by section and tell you where Oath-Bound departs, where it does not, and why. You do not need to read it cover to cover before you play. You need to know the differences that affect your character before you build one, and to have a sense of what the table will feel like once you sit down.

The first difference most players will notice is alignment. It is gone — not modified, not re-skinned, but absent. The PHB’s nine-point moral grid does not map onto a world where the gods are real, present, and have concrete positions on what you owe them and what they owe you. What replaces it is not a simplified version of the same thing but a different question entirely: not "what kind of person are you, cosmologically?" but "what have you sworn, to whom, and are you keeping your word?" The implications of that shift run through everything from domain mechanics to how NPCs assess you.

The second difference is in how divine characters — clerics, druids, paladins — relate to their gods. The PHB presents divine power as a daily transaction: pray, memorize spells, spend them, repeat. In Oath-Bound that model has been replaced by something with more structure behind it. Divine actors are instruments of institutions — Foundations, in the setting’s terminology — and their power is the operational expression of a standing relationship between that institution and its god. The cleric is not an individual with a direct line to the divine but a sanctioned representative of something larger, and what that means in practice is explained in the PHBO.

If you are playing a divine character, the flavor of that character is different in Oath-Bound in important ways. The mechanical differences are real but manageable, while the fiction is more substantially changed. An Oath-Bound priest has an institution, a code, and a set of obligations that run in both directions — not a restriction, but what makes the character interesting.

Most mechanical resolution in Oath-Bound uses percentile dice rather than a d20. As a player, what this means practically is that your character’s capabilities are expressed as percentages rather than bonuses, and that minor advantages and disadvantages have more granular expression than the d20 allows. The arithmetic is not complex, and the adjustment period is short.

Advancement works differently, and players should understand this before play rather than after. Oath-Bound does not use the PHB’s experience point tables in the conventional sense. XP is awarded solely by the GM when Closing The Rutter — the end-of-session act of recording what happened, whose accumulated entries are The Rutter itself — honestly, collaboratively, and transparently, with no formula tying it to kills or treasure. A character does not level up; they arrive at a point where they are functioning at a new level because the fiction has established that they are. The underlying level structure remains intact, and what has changed is the honest acknowledgment that the GM’s judgment was always doing the work — replacing the pretense of objectivity with a process that can be defended at the table.

For players, this means advancement feels different. It is not something that accumulates invisibly and triggers on a number but a conversation that happens in the open. Most players, once accustomed to it, prefer it.

The races and domains in Oath-Bound are recognizable but flavored by the setting, and the PHBO notes where the mechanics are as written and where they depart. Some domain features have been adjusted, some simplified, and a few replaced, with the changes explained where they occur.

The marker system used throughout the PHBO is explained in the Legend — read that before the main content.

— xxxMogadon, May 2026