Here is the full list of all 20 Age of Empires: Castle Siege (UWP) achievements worth 1,000 gamerscore.
Won 20 Multiplayer Battles
Looted 30,000 Food
Built a Stable
Upgraded an Archer Tower to level 5
Unlocked the Catapult from the Siege Workshop
Won 3 battles in the Historical Campaign
Unlocked the Ladder Invaders from the Barracks
Advanced to the Second Age
Successfully defend your castle 10 times
Destroy 30 Emplacements in Multiplayer Battles
Win 100 Crowns in Multiplayer Battles
Loot 100,000 Wood
Loot 60,000 Stone
Destroy the Keep 100 times in Multiplayer Battles
Unlock any 6 heroes
Unlock each civilization's unique troop
Destroy 40 Walls in Multiplayer Battles
Advance to the Eighth Age
Win 2000 Crowns in Multiplayer Battles
Fully upgrade each civilization's unique troop