What is your opinion about neutral creatures?

Yes, but not a Necromancer with 5 levels of Death Magic, or a Priest with a Guardian Angel. The Necromancer finishes off the sea creatures with Death Touch, and the Priest casts Guardian on the angel and sends it into battle.

I agree, and the fire creatures are like salamanders (in Heroes 5).

But if there are 20 sea creatures, and a non-critical hit can only kill 7, then what?
The monster just bites him - the non-critical hit is gone, the Guardian Angel raises the body and immediately falls due to being absorbed!

And the Guardian, even if it manages to activate, might not work at all, and there won