The first things that come to mind:
- Dwarves (because mages are not just about magic, but also about the pursuit of knowledge. Dwarves are also inventors).
- Witch Hunters (an anti-magic unit in a magical castle).
- Soldiers in armor, of the same race as the mages themselves – that is, humans. Otherwise, it seems strange that everyone is a mage. Perhaps some don't have the gift or the money, or something else. There must be ordinary mortals...