Here is the full list of all 21 Space Crusaders achievements.
Survive 5 minutes in The Castle
Survive 10 minutes in The Castle
Survive 15 minutes in The Castle
Kill 25 Fast Skeletons
Kill 100 Fast Skeletons
Kill 500 Fast Skeletons
Kill 10 Enemies
Kill 100 Enemies
Kill 1000 Enemies
Kill 1 Skeleton Mage
Kill 25 Skeleton Mages
Kill 100 Skeleton Mages
Kill 10000 Enemies
Die Once
Die 5 Times
Die 25 Times
Survive as the Priest for 5 minutes.
Survive as Sheldon for 5 minutes.
Survive for 7 minutes in The Castle
Survive as Slayer for 8 minutes.
Survive as the Priest for 10 minutes.