AA (1. Alphatian Artifact; 2. Alfheim Avengers). 1. Artifacts found only in the AS after Alphatia's sinking. 2. Young AE staging terrorist raids on SE after Alfheim's takeover.
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.
AI or AoI (Arm of Immortals). Region linking western Brun and DV.
AS (Alphatian Sea). Region east of the KW where Alphatia resides.
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.
BoR (Brotherhood of Radiance). Clique of Immortals dedicated to pursue researches on the Radiance during WotI.
BoS (Brotherhood of Shadow). Clique of Entropics dedicated to making WotI last as long as possible.
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).
CoK (Church of Karameikos). One of the two main churches of Karameikos.
CoM (Champions of Mystara). Campaign extension describing the area between the KW and the SC, and skyships (OD&D).
CoS (1. City of the Stars; also 2. Chamber of the Spheres). 1. Capital of the SE. 2. Rafiel's Reactor.
CoT (1. Church of Traladara; 2. Church of Thyatis). 1. One of the two main churches of Karameikos. 2. The main church of Thyatis.
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).
DV (Davania). The southern continent.
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).
GC (Greater Carnifex). Beings that lived on Mystara long ago and challenged the Immortals; were banished to the PoB.
GM (Great Migration). Humanoid migration questing for the Blue Knife in the MA.
GRoF (Great Rain of Fire). Event that destroyed Blackmoor and altered the world axis.
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 east of the KW.
JA (Joshuan's Almanac). Book describing the KW and one year of events (AD&D) (AC 1013).
JC (Jungle Coast). Region of DV.
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 PoV), 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).
MA or NA (Mystaran Almanac or Net Almanac). Series of electronic books describing the world and one year of events each (AC 1014 and beyond).
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).
OB (Outer Beings). Powerful evil beings that warred against the Immortals long ago but are now imprisoned in an outer plane.
OD&D or D&D (Original or Old D&D). Old D&D, as opposed to AD&D.
OW (1. Old World; also 2. Outer World). 1. KW; also 2. surface world as opposed to HW.
NW (Norwold). Region north of the KW.
PoB (Pits of Banishment). Plane where the GC were confined to by the Immortals.
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 each (OD&,D and AD&D) (AC 1010-1012).
RC (Rules Cyclopedia). Compilation of the old rules, with Mystara extension (OD&D).
RoF (Ring of Fire). Clique of Immortals dedicated to stop researches on the Radiance during WotI.
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.
SD or SoD (Sea of Dawn). Region east of the KW centered on the IoD.
SE (Shadow Elves). The underground elves of the KW.
TM# or ETM and WTM (Trail Map#). Trail maps of the Eastern and Western 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).