How do you create your own creatures in Heroes of Might and Magic V: Tribes of the East?

Dude, to add a new creature in HoMM V, you need a new ID. You can't add it without modifying the .exe file.

Yes, I understand that I'll have to modify the .exe file. I've even already opened it with WinHex, but I can't figure out how to navigate it. Some parts show gibberish, while other parts show understandable parameters that can be changed. Is there a guide on how to work with the .exe file?