Using Mystara Gazetteers with OSE: Rules You Need to Check
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GAZ10 adds humanoid PCs; Darokin adds a merchant class. Review regional character options separately from maps and factions when using Mystara with OSE.
Mystara Gazetteers can supply a world for Old-School Essentials without requiring every optional rule printed in them.
Use a regional book's places and factions as setting material. Review its character classes and other procedures separately, against the OSE rules your group actually uses.
Compatibility begins with the kind of material
Necrotic Gnome's official adaptation guidelines explain the broad cross-compatibility of games derived from Basic/Expert D&D. That supports using older material with OSE. It does not make every BECMI supplement a rule already present in the OSE core. Divide a Gazetteer into setting facts and procedures. A border, ruler or faction can enter the campaign without a conversion formula. A new class needs advancement and ability rules. A naval-combat procedure needs agreement about how ships and crews are represented. Those decisions can be made independently, so the extra rules need not block use of the setting.
| Gazetteer | Material identified by its publisher description | Decision for an OSE campaign |
|---|---|---|
| GAZ1, Karameikos | Regional history, settlements, people and maps. | Use it as a location reference; check mechanics in the passages you import. |
| GAZ3, Glantri | Magical study, research and the Seven Secret Crafts. | Decide whether those magical procedures are available to PCs. |
| GAZ4, Ierendi | A sea-battle method with ship counters. | Choose it or your existing naval procedure before staging a fleet encounter. |
| GAZ7, The Northern Reaches | Runic magic. | Review how it interacts with the campaign's spellcasting. |
| GAZ8, The Five Shires | A new halfling class and halfling magic. | Determine which halfling rules a player uses from creation onward. |
| GAZ10, The Orcs of Thar | Humanoid PCs, spellcasters and the separate Orc Wars game. | Approve any PC rules explicitly; distinguish the boardgame from character combat. |
| GAZ11, Darokin | A merchant class. | Review its full class rules before adding it to the available roster. |
| GAZ12, Ethengar | A shaman class and warfare material. | Check both the class and any warfare procedure you intend to adopt. |
| GAZ13, The Shadow Elves | Shadow-elf character rules and shamans. | Read those entries instead of assuming ordinary elf rules cover them. |
| GAZ14, The Atruaghin Clans | The Shamani class and character-creation material. | Make its availability a separate decision from using the regional map. |
This checklist selects additional material named in the linked publisher descriptions. It is not an exhaustive GAZ1-14 rules index. A book absent from the table is not certified to contain only setting lore.
A regional character is not automatically a new class
A character can come from Darokin without using the Gazetteer's merchant class. Likewise, a Glantrian magic-user can live in that society while the referee postpones access to its special magical procedures. Preserve the setting identity even when you leave a rule module out.
For a class you do import, compare its experience table, maximum advancement and spell access with the rules in use. Record how its abilities are resolved. Where an OSE Advanced Fantasy campaign separates race and class, decide how you will present a Gazetteer option written with different assumptions. Do that before a player invests in the character.
Keep named NPCs at the level appropriate to their role. A ruler's influence need not become an ordinary OSE PC progression just because the party can meet that ruler. If a high-level NPC must enter combat, prepare its capabilities explicitly rather than treating a title such as "wizard-prince" as a stat block.
Choose one skill procedure for imported options
When a Gazetteer passage offers a skill or special check, write down the triggering situation and the roll it calls for. Decide whether to preserve that rule, use the campaign's existing procedure or omit the option. There is no need to import a new general skill system just to use a location description.
A useful campaign note has a source reference, the decision and one example of application. "GAZ rules allowed" leaves the method open. "Use the published rule for this named skill" gives players something they can consult.
Prepare one region before the whole series
- Pick the party's starting location and read the player-facing material separately from the DM's secrets.
- Prepare the immediate map, local factions and people likely to appear in play.
- Approve only the additional rules players can use now. Keep a source reference for each choice.
- When the campaign expands, check the next region's procedures on their own terms. A previous approval does not establish that every Gazetteer option works identically.
High-level dominions and armies are a different problem from regional character options. The CM1 and M1 guide covers that boundary. The complete Gazetteer catalog provides the regional product records.
Sources and scope
Publisher compatibility statement: Necrotic Gnome's linked adaptation guidelines. Regional content: the linked original TSR publisher descriptions preserved in the archive. The campaign decisions are suggested preparation steps, not claims that every additional class has been converted or playtested.