The Game
Approaches to Playing AD&D (p.9) 
| The vanilla DMG describes a range of approaches to play, from pure storytelling to realism-simulationist. Oath-Bound sits firmly outside the realism-simulationist end of that spectrum — and deliberately so. The intellectual biography behind the design is covered in the Designer Diary. The short version: extensive experience with simulationist systems produced the conviction that the mechanical apparatus was doing less work than it appeared to, and that the fiction was the point. |
The DMG’s characterization of play approaches is substantially accurate as a map. Oath-Bound simply occupies a specific position on it and has opinions about why.
Dice (p.9) 
| Oath-Bound adopts a d100 percentile resolution system as its primary resolution mechanic — the most structurally significant departure from vanilla AD&D in this overlay. The system, its rationale, and its practical application are covered in full in the CRM. |