Ever since you were a hatchling, your master took good care of you. He's long gone now, but you still live in his tomb. The least you can do for him is to protect it while his servants prepare a complicated spell to seal it. One day, you're sleeping on the rug, when suddenly, the doors open and a group of adventurers come in to steal your master's treasure! Protect it at all costs!
Blizkenripper is way too hard to kill for humans let alone the AI. When you stock up two armors in your hand you can't really be hurt aside from the punishing and penetrating attacks. I think it might be more fun if you designed it around Xanthicius who is much harder to defend with and used a weaker set of enemies to compensate. Preferably ones that don't automatically fold to Rockfall.
Rockfall is a major issue. The melee characters can't reach you and the wizard doesn't use offensive attacks. I think you should use a more dangerous wizard and make sure each character has some way to bypass difficult terrain. Or maybe rethink the starting placements so that the victory points are more accessible for the AI.
Still pretty easy, you can win just by staying back and playing Rockfall and Corrosive Breath. And the victory squares are pointless if you need 50 stars to win.