<cough> What? Oh, yes.
So I don't know that you can really call it reverse engineering with the JG Wilderlands maps because the listings in the atlases are pretty straight forward. You just have to figure out where they got the result. You can look at the JG tables and see what I mean. The table mechanics will be in boxes below.
Each of the big Judges guild maps (Wilderlands of High Fantasy being the first) has approximately 1842 hexes spread across it's 48"x36" Arch E size at a scale of five miles per hex.
I loosely totaled the number of locations listed in each atlas (encounters) and came up with a rough chance of 1 in 6 to 1 in 8 of there being an item of note in each hex. The more populated maps were closer to 1 in 6 and the more sparsely populate maps or those with a lot of water had closer to 1 in 8 of incident per hex.
This roughly lines up with the normal chance of encounters rolled on a d6 in OD&D. The JG maps just took the concept of a DM rolling for each new hex and generating it ahead of time.
Note that this method does not generate any geography, just random encounter locations.
Civilization Density of Map |
Chance of Encounter Location |
Populated |
1 in 6 |
Medium |
1 in 7 |
Sparse |
1 in 8 |
There are five different types of encounter locations listed in the atlases. With a weight towards villages and castles in populated areas and Lairs and ruins in sparser areas. Islands are naturally a different case.
d8 |
Land Encounter Location Type |
1-2 |
Village/Town/City |
3-4 |
Citadels & Castles |
5-6 |
Lurid Lairs |
7-8 |
Ruins & Relics |
Note |
Modified -1/+1 for populated or sparse regions |
d6 |
Water Encounter Location Type |
1-3 |
Idyllic Island |
3-5 |
Open Water |
6 |
Sunken Lair? |
Once the DM has determined the rough encounter location, they can move it to an adjacent hex if the geography can suit the given encounter better. (Moving a castle next to a river, moving a lair from plains to hills.)
For each type of encounter location, various JG tables are used.
Encounter Location |
Development |
Village/Town/City |
Randomly determine the name, politics, population, buildings and features of note using the JG Villages tables. Determine the alignment and race of the population using the "Castle Leader" tables in the JG Castles book. Map the village or pick a generic village map from the JG Village book. The village tables only can create small villages with small populations. JG suggests larger towns are made custom. More tables can work here. |
Citadels & Castles |
Use the JG Castle tables. Map the castle or pick a generic castle from the JG Castles book. |
Lurid Lairs |
Roll on the OD&D wilderness encounter table, modifying for any geographic terrain. If the monster has a "in lair" percentage, then it has a lair in the hex. Reroll on the wilderness encounter table if the monster does not have an "in lair" above 0%. Map the lair and pupulate as a dungeon with the wilderness encountered monster as primary resident. Fill the rest of the dungeon as needed. The crazy JG caves and caverns tables can be used but they often produce "real" caves that stretch forever in long straights. AD&D dungeon generation also works. (JG never made such a "normal" dungeon table) Treat as full adventure location if monsters warrant |
Ruins & Relics |
Roll on the JG ruins & relics to find what is guarded and by what type of monster. Create a dungeon and have the primary resident be the guards. Random cave & dungeon tables work here or the ruin can be indicated as covered by leaves or other "non-dungeony" descriptors. Lots of interpretation. Treat as full adventure location. |
Islands |
Roll on the JG Idyllic Islands table. |
The DM then takes all the encounter locations and tries to divine political boundaries, roads, and trade routes by looking at the alignment and races that occupy the castles and villages. Each encounter location should have about five hooks (village rumors, jobs, legends) with adjacent encounter locations.
Custom wilderness encounters could be made if you want. I recommend that there is a roll for wilderness encounters as normal when the party is traveling through hexes as normal, but no results of a "lair" encounter.
I have made these maps but their actual play is still theoretical. (C'mon, this is hundreds of encounter locals at a time for a full JG map. I am just working out details for a home base area so far but I have a reference to all the alignments and populations of surrounding towns. It makes for some narrative acrobatics, like figuring out how all these troll, ogre, gnoll, and orc villages survive.)