Seems like an event to the veterans and not the newbies. Sorry to the new player trying out this game, but this event will ruin you.
6 days to get 6 heads. That's fine I guess but the best chance we have in each attempt is 40%
In Dyme, I have the troops and resources to make attempts at a 40% chance of success. I am fairly certain I will complete the 6 heads and receive the bonus. ( which is not needed )
In Lapithos, I just started. I have made several attempts with as little troops as I could spare ( with a lower % chance of success ) I could go for the 40% chance of success however it would take me 80 troops. Everyone keep in mind what 80 troops means to you while in beginners protection or even just coming out of it. People are already waiting for you to come out of BP so they can farm you or take your real estate, or you are utilizing those troops in the tutorial or the bandit camps to progress. So the question from the newbie is do I send away troops to likely die and get next to nothing in return OR do I keep them and defend my sole city the best I can when the impending attacks come. But, that PRIZE looks so nice! I guess I just came to this game late so I will likely go play something else. That's what's in the mind of the beginner.
Sadly the people that think this stuff up don't seem to get it. New players are hard to get and even harder to keep. This event will more than likely drive them away. I would recommend rewards more appropriate to city count, age of world and other various factors. THINK people