Here is the full list of all 20 Age of Empires: Castle Siege (Windows) achievements worth 200 gamerscore.
Unlocked the Catapult from the Siege Workshop
Won 100 Crowns in Multiplayer Battles
Won 3 battles in the Historical Campaign
Won 20 Multiplayer Battles
Looted 30,000 Food
Unlocked the Raiders from the Barracks
Advanced to the Second Age
Successfully defend your castle 10 times
Destroy 30 Emplacements in Multiplayer Battles
Upgrade an Archer Tower to level 5
Loot 100,000 Wood
Loot 60,000 Stone
Destroy the Keep 100 times in Multiplayer Battles
Unlock any 6 heroes
Build a Stable
Unlock each civilization's unique troop
Destroy 40 Walls in Multiplayer Battles
Advance to the Eighth Age
Win 2000 Crowns in Multiplayer Battles
Upgrade all civilizations' unique troop to level 4