Troop buildings, the first order corresponds to ordinary one-star troops, the second order corresponds to ordinary three-star troops, and the third order corresponds to rare one-star troops.
The highest seems to be seventh-order.
However, there is no record of seventh-order buildings. Even in Dragon Courtyard, an area where several major countries jointly station troops with intense disputes, there are only sixth-order Dragon Nests.
In the sixth-order area, basic recruitment can obtain excellent three-star troops, and there is a chance to trigger an epic life form.
And such sixth-order troop buildings can recruit batches repeatedly after a period of time, so it's no wonder that all major countries strive to commandeer them.
This is already related to the foundation of the country.