Here is the full list of all 19 Castle Invasion: Throne Out achievements worth 1,000 gamerscore.
Fully Upgrade the Crossbow
Defeat the King's Troll
Collect 50 Stars
Complete a Night Level
Defeat the King's Dragon
Unlock the Spear
Collect 3 Stars in a Time Level
Defeat 50 Dwarves
Complete Level 1
Defeat the Evil Archer
Defeat the King's Commander
Defeat the King!
Fully Upgrade the Bow
Fully Upgrade the Spear
Unlock all Upgrades!
Hit Every Enemy Type With the Spear
Knock a Dwarf Off a Hog
Collect 100 Stars
Collect 150 Stars