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