They are rewarded during KvKR events, personal and clan... Check the different goals to see where they're at

during the last kvkr you could get them in personal achievements checkpoint 1 & 2 gave you 1x 1 hour domain guard each and check point 3 gave you 1 x 3 hour domain guard, but your kingdom needs to win the kvkr for you get get the personal achievement rewards.but the personal rewards change so not all kvkr events give them its best to take a look at event info