fun idea
But what's the point of the princess? I mean, the idea is cute, that you're killing the hero instead of helping him save the iconic damsel in distress. But he can't anyways, so there's no unique challenge there.
On that note, it's not the point of the game to keep him from saving the princess, or even killing him. The game is basically "feed the knight to the monster."
It's fun, but you took an idea and made a different game out of it.