Final answer:
The phrase "King by the Grace of God" was important during the Dark Ages as it represented the Church's claim that kings ruled by divine right, making it more difficult for anyone to challenge their authority.
Step-by-step explanation:
The phrase "King by the Grace of God" was an important statement during the Dark Ages because it represented the Church's claim that kings held their position because it was granted to them by the pope. This phrase helped legitimize the power and authority of kings, as it implied that their rule was divinely ordained. It also conferred religious legitimacy to monarchs, making it more difficult for anyone to challenge their authority.