Here is the full list of all 12 Defenders of Ardania achievements worth 200 gamerscore.
Complete all levels in Limited Resource mode.
Finish the Campaign.
Use all Economy Upgrades in one mission.
Win a level without towers.
Use the unit info 10 times.
Win 5 multiplayer match in a row.
Sell 10 towers in a single mission.
Finish the first mission.
Build all tower types of one race in one mission.
Survive 60 waves on the Survival game mode.
Destroy the Minotaur Base.
Unlock all achievements.