Age of Empires Online

Around the time you reach level 10, Agamemnon, the king of Mycenae, will appear in your city to give you quests. The very long, but also very fun (and sometimes very difficult) quest chain begins here. From the quest line in your city he'll move to Mycenae and ask for some more help in the last few quests which involve the kidnapping of Helen. From there it's off to Troy where you'll be swapping back and forth between quests from Agamemnon and Odysseus. Some of these can be very difficult solo, but in general there is usually one or two side routes on every map to sneak up behind the enemy, or around the enemy when necessary. Anyway, once that last chain of quests is done you will be tasked to lay siege on Troy itself, which will reward you with both the epic feeling of taking over a city, and the blueprints for the Trojan Horse (which requires no materials).