The final part for the September update involves  the Creature Compendium, although the Changelog is significantly shorter than tthe others.
Additionally the Core Rules and Adventure Compendium got some small fixes, aka some errors corrected here and there

Creature Compendium:
- Added rules for Mobs of weak creatures
- Added the Hypnotrice, Jaguar, Leshen, Sabitians and Servus Malus Fighter
- Changed the document format from Letter to A4