Solo modules developed for the Dungeons & Dragons Basic Set and Expert Set, respectively.  

MSOLO1 Blizzard Pass by David Cook
MSOLO2 Maze of the Riddling Minotaur by Jeff Grubb

Both these were assigned the "M" module codes seemingly without much forethought.  When the D&D Master Set came out a few years later, TSR apparently decided to go ahead and re-use the M codes for its Master modules.  To dispel this confusion, we'll refer to these modules using the MSOLO codes, even though they were never actually assigned or printed with them.

Both modules come with "magic pens" (either with a blue or yellow cap), which reveal "hidden" text blocks depending on your choice of actions.  As such, they are pretty much single-use only.  TSR attempted to solve this deficiency with their later solo module, MV1 Midnight on Dagger Alley, which uses a red-plastic "magic viewer" instead.  Interestingly, most (all?) foreign editions of the MSOLO modules also use this "magic viewer".

The missing entries of MSOLO1 Blizzard Pass can be found here.  Thanks to Benedict Lnu for the transcription, and to Paul Viveiros for converting the text entries to Interactive HTML!

The missing entries of MSOLO2 Maze of the Riddling Minotaur can be found here.  Thanks to Vince Lethal for the transcription, and to Paul Viveiros for converting the text entries to Interactive HTML!

Contributor Daniel Thingvold notes that the entries to both modules can be revealed by a standard black (ultraviolet) light.

Printing Information

MSOLO1 Blizzard Pass
First:  Angled TSR logo. Second:  Identical in all respects to the First print, but affixed with a red cardboard header on top of the module, with the D&D logo and some other advertising.  Note that without the header, this print would be indistinguishable from the First print.  Further info on header modules is here.
MSOLO2 Maze of the Riddling Minotaur
First:  Angled TSR logo. Second:  Identical in all respects to the First print, but affixed with a blue cardboard header on top of the module, with the D&D logo and some other advertising.  Note that without the header, this print would be indistinguishable from the First print.  Further info on header modules is here.

Because of the included "magic pens" (attached on the side of the front cover with a piece of Velcro), and the one-use text blocks, these modules are only rarely found in true-mint or shrinkwrapped condition.

• MSOLO1 Blizzard Pass
• MSOLO2 Maze of the Riddling Minotaur