Here is the full list of all 12 Castle Chaos achievements.
Defeat a team of three hard AI opponents.
Succeed in repairing your castle walls by controlling a gnome.
Three human players team up against a hard AI opponent.
Destroy all castles of an opponent.
100 gnomes killed.
Kill a gnome just before he places a bush.
Defeat one or more AI players on difficulty setting "Medium".
Defeat one or more AI players on difficulty setting "Hard".
Defeat three AI players on the "Hard" setting.
Capture all castles in your kingdom
Defeat one or more AI players on difficulty setting "Easy".
Start a match in Castle Chaos