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