Age of Empires Online is getting a skirmish booster pack. These paid-for bolt-ons normally add new races and missions, but this one will introduce a new mode that will let you and your friends fight a team of tailored AI opponents to gain XP and upgrades. The greater the odds you face, the more loot you'll get.
The skirmish mode will also unlock all of Age of Empires Online's units for you to play with, even if you're at level one. It should be a good way to road test powerful units that you wouldn't otherwise see for hours. It's an interesting add-on to the intriguing free to play online RTS. If you'd like to try it, you can download the client from the Age of Empires Online site and start playing now.