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