AC or A.C. (After Crowning of the first Emperor of Thyatis). To calculate dates according to the Thyatian calendar.

AC# (Accessory #). Series of adventures and rule supplements (OD&D). The PWAs also have AC as a code (OD&D and AD&D).

AE (Alfheim Elves). The main group of surface elves of the KW.

AY or A.Y. (Alphatian Year). To calculate dates according to the Alphatian calendar.

B# (Basic #). Series of adventures for basic level of play (OD&D).

BC or B.C. (Before Crowning of the first Emperor of Thyatis). To calculates dates according to the Thyatian calendar.

CAS (Clark Ashton Smith). Author of short stories that have inspired Mystara's Nouvelle Averoigne.

CM# (Companion #). Series of adventures for companion level of play (OD&D).

CoM (Champions of Mystara). Campaign extension describing the area between the KW and the SC, and skyships (OD&D).

DA# (Blackmoor #). Series of adventures set in the Blackmoor era (OD&D).

DDA# (Challenger adventure #). Series of adventures set in the KW (OD&D).

DDC (Darokin Diplomatic Corps). Darokin's network of diplomats and spies.

DMR# (Challenger rules #). Series of rules supplements (OD&D).

DotE (Dawn of the Empires). Campaign extension describing the empires of Thyatis and Alphatia (OD&D).

G:KoM (Glantri : Kingdom of Magic). Campaign setting (AD&D).

GAZ# or Gaz# (Gazetteer #). Series of books describing the countries of the KW (OD&D).

HK (Heldannic Knights). Knights of Vanya that rule in Heldann.

HW (Hollow World). The inner world of Mystara.

HWA# and HWQ1 (Hollow World Adventure #). Series of adventures (OD&D).

HWR# (Hollow World Rule #). Series of campaign extension (OD&D).

IM# (Immortal #). Series of adventures for immortal level of play (OD&D).

IoD (Isle of Dawn). Region of the KW.

JA (Joshuan's Almanac). Book describing the KW and one year of events (AD&D).

K:KoA (Karameikos : Kindom of Adventure). Campaign setting (AD&D).

KPE (Karameikan Polar Expedition). Expedition that went to the HW and back.

KW (Known World). In earlier OD&D products, the region of the world that had been mentioned in module X1. Later refers to the area described in the GAZs, or, more generally, the "civilized" area of the world (from a Thyatian point of view), ranging from the Sind Desert to Alphatia.

M or M- (Mystara). Prefix commonly apposed to our real world names to make temporary equivalents for the world of Mystara until they get a new name (e.g. MOrient).

M# (Master #). Series of adventures for master level of play (OD&D).

MML or mml (Mystara Mailing List). Where Mystarans discuss the world.

MoA (Mark of Amber). Adventure (AD&D).

NACE (New Alphatian Confederate Empire). Name of the empire that succeeded the NAE.

NAE (New Alphatian Empire). Name of the remains of the Alphatian Empire after Alphatia's sinking.

NoS (Nucleus of Spheres). Artifact, source of the Radiance.

O# (One-on-one #). Series of one-on-one adventures (OD&D).

OD&D or D&D (Original or Old D&D). Old D&D, as opposed to AD&D.

PC# (Creature Crucible #). Series of campaign extensions for monster races as PCs (OD&D).

PWA or PWA# (Poor Wizard's Almanac #). Series of books describing the world and one year of events (OD&D and AD&D).

RC (Rules Cyclopedia). Compilation of the old rules, with Mystara extension (OD&D).

RS (Red Steel). Name of the setting describing the SC. Also, the name of a substance found only there (AD&D).

SA (Schattenalfen). The underground elves of the HW.

SC (Savage Coast). An area of Mystara west of the KW suffering from the Red Curse.

SE (Shadow Elves). The underground elves of the KW.

TM# or ETM and WTM (Trail Map#). Trail maps of the Eastern and Werstern KW (OD&D).

ToL (Tree of Life). Living artifacts of the elves of Alfheim, incarnations of Ilsundal.

WDL (Western Defense League). Association of some states of the KW.

WotI (Wrath of the Immortals). Adventure and campaign extension describing events from AC 1004 to AC 1010, and the Immortals (OD&D).

X# and XL1 (Expert #). Series of adventures for expert level of play (OD&D).

XS# and M# (Solo #). Series of solo adventures (OD&D).