1. Dierna was a customs station which was granted municipium status by Septimus Severus.

2. Septimus : Oh yes, when I tell him that the Bishop DID die by your poisoned grog.

3. Septimus will be here by the morning, find the girl, get the stone and be king forever

4. They were probably created to top a triumphal arch or some other grand building, perhaps commissioned by the Emperor Septimus Severus.