Visiting Preserves and Hives is prohibited.
It happened to me in one game. I ate 3 Dragon Utopia, while my opponent ate only one, and after that, he surpassed me in stats.... You could also say: FREE STUFF! But still—it's a game and there's nothing you can do about it; the element of luck cannot be removed from Heroes! Just like with cards, if four aces come up, what do you do now? ;)
And for those who want to win solely through skill, I can suggest 2 options:
1. Play offline
2. Play chess
:D