Here is the full list of all 16 Heidentum achievements.
Start the tutorial.
Finish the tutorial.
Destroy a temple.
Destroy THREE temples in one game.
Slay ONE HUNDRED monsters.
Slay ONE THOUSAND monsters.
Slay ONE HUNDRED units.
Slay ONE THOUSAND units.
Win a game.
Win TEN games.
Win a game playing as Germans.
Win a game playing as Greeks.
Win a game playing as Egyptians.
Win a game playing as Christians.
Get a rank for yourself.
Become a legend.