Current questions and answers regarding the map editor.

I checked again: the game doesn't launch with the Creature folder. It displays the error message mentioned earlier, stating that the original version of HoMM V cannot be found.

It's best to test it on a clean game installation.

I understand why the game doesn't launch with the Creature folder. The reason is that this map is designed for the "Universe" modification, if you're familiar with it. Consequently, that's why the game doesn't start for you.
The mod has its own executable file and data pack.