Age of Empires Online

For this achievement you must complete the quest "The Sack of Delphi," which can be found in Tylis.
The basic idea is to build a large siege army and assault the enemy base, destroying the Temple of Delphi in the process. The biggest problems come with the fact that your allies can be useless, and the enemy will have many priests to convert your allies. In order to counteract the conversion of your teammates, and your own units, you'll want to plant a fortress near the temples in your first rush to clear out any priests that spawn, and allow you to regain any lost units and assault each building individually.