From the Introduction:
Welcome to the Mystara 4E Creature Compendium (M4E2). This is a massive compilation of Mystaran creatures converted to Fourth edition D&D. Sources used included the Rules Compendium, the Gazeteer series, and various Classic D&D monster supplements. It sticks to creatures unique to Mystara or to Classic D&D or versions of monsters found in other editions of the game which are found in Mystara.
You will find 190 Heroic Tier, 76 Paragon Tier, and 26 Epic Tier monsters within this volume. This includes several famous Mystaran NPCs, including King Doriath of Alfheim, Duke Stefan Karameikos, Alfric Oderby of the Church of Karameikos, Bargle the Infamous, and of course, Baron Ludwig von Hendriks, the Black Eagle Baron.