Supplement I: Greyhawk

The first supplement to the original Dungeons and Dragons first edition. To quote the forward by Gary Gygax:
"There are new characters, new abilities, more spells to use, a horde of new monsters, heaps of new magical treasure, and various additions to the suggestions and rules for adventuring above and below ground."

This supplement introduces the Thief as a character class and Paladins as a sub-class of Fighting Men.