The game doesn't allow for mixed neutral creatures.
And I definitely don't understand why an oasis needs to be disguised as a well. Of course, this is a matter of taste, and it might appeal to some, but I'm more than sure that true connoisseurs will mostly disapprove of such a blatant replacement of objects.
Added 20 minutes later
But the combat aspect is impressive right from the start. One battle with 6 green dragons against me is more difficult than half the battles on the Haven map (or maybe I was just being dense and didn't see the obvious solutions). I hope everything will be even darker further on.