Sacred units can be blessed by priests or the presence of a pretender during a battle in their own dominion. This causes the units to gain +1 morale, as well as all the effects of the pretender's bless that were chosen at the beginning of the game, plus additional effects gained from certain claimed thrones. They also have a halved upkeep cost compared to a non-sacred unit of the same gold cost.
Prophets are always blessed, even on the strategic map. Pretenders and disciples are always blessed in friendly dominion. Additionally, the allows a non-sacred commander to become permanently blessed.
When blessed, the sacred icon changes to a form with lit candles.