Solar Watch

The Solar Watch spend most of they're lives on ships, patroling Terra's solar system looking for theats the planets local defenses can't handle. The only exceptions are Terra itself since the regular Custodes got it covered and Mars because they trust the Mechanicus. If there is a threat reported in a nabouring solar system, they'll quickly go handle it as quickly as possible before returning to Terra's. If there is trouble in a solar system further away then that, thats not they're problem.

The Empress won't allow Custodes to join the Solar Watch unless they have a large harem to go with them. This serves 2 purposes.

1. It allows her to keep collecting power from them even though they're on ships most of the time.

2. Stress relief.