In the on-line help file for Thexder 95, they make mention of an add-on called "Thexder Extras":
Available January, 1996
A supplemental on-line Help file that contains all the information you need to get through each level of Thexder plus an editor to create your own new levels to challenge yourself and your friends plus lots of new map levels to play. A real value and a great addition that makes Thexder even more fun! Included are the following:
This part of Thexder Extras gives you the secret codes to increase your ammo, equipment, energy charges, and energy cells (extra lives). It's as easy as typing phrases from your keyboard. Now you can get past those levels that are just a bit too tough.
Having trouble getting past one of the techies? Can't seem to avoid that lava pit? Can't find the hidden path to a new location? Use this section of Thexder Extras to find the most efficient weapon to eliminate that techie, the best form for Thexder in some locations, and where to find hidden weapons and equipment. Find out each techie's pattern of movement and when he is vulnerable to your attack.
Maps and Solutions
The third part of Thexder Extras illustrates graphically a successful path through every level and shows hidden shootaways and foreground cells. Find the locations of hidden ammo and equipment, and read hints on how to get to them.
Create new levels for any world to surprise and challenge your friends. This is the development tool used to create and decorate all of the levels in Thexder. Have access to the special tiles for walls that you walk behind instead of bumping into, shoot-away tiles, platforms, switches, lava, acid, caves, conveyers, and invisible floors and walls.
Brand new levels have been created for those who just can't get enough of this robot. New ideas, new challenges, and new puzzles are all available to challenge you at any difficulty. Explore the new ice caves, race along the girders of Geigerus, or find your way through the the caves of Chaox. An absolute necessity for all Thexderites.
How to Order
Cost of Thexder Extras is $14.95 plus shipping and handling.
For more information call 1-800-757-7707 or contact Sierra via World Wide WEB at http://www.sierra.com
Periodic searches using Google, the Internet Archive, Ebay and MobyGames over the years haven't revealed any information as to the existence of this mysterious add-on pack.
At the cost of $14.95, I'm not sure if it was to have been distributed on diskette(s) or on a CD-ROM ...
Does any know if it was ever released? Or did the sales numbers for this edition of Thexder and not-so-glowing reviews at the time prevent that?
I'd certainly love to find a copy of it somewhere, if only to sneak a peek at cheat codes that would actually work for this game...
Thanks for listening and any help you can provide.