philosophy

There can only be one Empire. Two Empires cannot coexist in the same world. And therefore, the Griffin Empire will always fight against any race that dares to create its own Empire. Not out of fear, not out of hatred, but simply because a second Empire undermines the very essence of an Empire. The essence of an Empire is the opposition between the Empire and the rest of the world. So, humans are not so honest and noble. They are imperialists, and that says it all!

No need to make things up. Give me just one example from the history of Heroes 5 where humans attack the undead?

Added 4 minutes later

Quote (Nowizard): "It's a different story with the Empire: the most important things in their lives are honor, courage, friendship, and bravery. They never attack anyone first, always striving for peace and prosperity."

Well, that's news! The bitter truth is that everyone attacks everyone else FIRST! That's the point of the game. Attack first, or you will be destroyed by those around you. It doesn't matter at all which race you belong to. Everyone is an enemy to everyone.

What you said is the philosophy of the USERS (us), for whom it is really much easier to gather a large army and defeat a less fortunate user who hasn't even learned how to play properly than to form an alliance with him (even if he is twice as weak as you) and help him against other users who are also not averse to "feasting" on newbies.
And also: throughout history, demons, mages, humans, and the undead have been the ones who attacked first. Demons attacked for the sake of war itself, mages because they envied necromancers (although, what is there to envy?), humans for the sake of the greatness of their country (they did what they considered right, and power has changed since then), and the undead attacked first in the campaign, and in the most insidious way. Through deception, treachery, and discord.

P.S. It turned out to be funny. The only ones who turned out to be innocent in this regard are the elves :D

P.P.S. Although, the dark elves also attack first. And quite often. Instead of strengthening their homeland, they only destroy it by starting civil wars.