Heroes of Might and Magic V [Game Discussion]

I found a lot of pictures with captions on the internet, something like "Mive's death at the hands of an angel-demoness."
And so on.
As far as I know, Mive is one of the basic heroes of the Haven faction in Heroes 5.
I also saw a screenshot directly from the game where Ravenna said, "Proud of my work. I'm no longer a mage." And I didn't know that she TURNED OUT to be a mage.
So, since there are such pictures, maybe there are some in-game moments that few people know about? Please explain.