I played a game developed by TenCent LTD out of China. It cost 30 Euros to play, one time payment and was limited to 50,000 players. It started when the 50,000 players registered. It was one versus one and no alliances in the format. You had to option to take prisoners or kill them. One real life day was one year of the world / 2 hours real life was a month and divided on down. There were several ways to travel, through the woods, plain, mountains and ocean. Weather was a factor to be considered etc as was food and population for soldiers / farmers / breeders. It was fairly complicated and a calculator was needed to co-ordinate attacks and waves of attackers. Also, ambushes along the travel routes could be set up. Cities had a value based on their production capabilities for food and weapons and strategic location. The game ended when the Emperor died...an unknown, but usually less then 3 months (90 days or 90 years in the game).
There were cash prizes returned to your credit card depending on where you placed in the final valuation at the time the Emperor died. As the company took in 1.5 million euros for one game round it paid out 250,000 in cash prizes to the top 1000 players. Players started cheating by using internet connections outside the game such as SKYPE and emails. They shut it done due to that.