Holy Knights

The Holy Knights (聖騎士 Seikishi) are the most powerful knights in Britannia who are heroes that protect the kingdom. They are a group of terrifying individuals, with each able to match an entire country's army in strength and power, and having magic that transcends human knowledge imbued within their bodies.

In Britannia, there are orders of Holy Knights within the kingdoms of Liones, Camelot and Danafor (before it's destruction).

10 years ago
When the Seven Deadly Sins were framed for killing the Great Holy Knight, Zaratras, and plotting to overthrow the kingdom, the entire order of Liones' Holy Knights were dispatched to kill them all. After the group of knights' supposed offense and the subsequent escape of at least four of them, the Seven Deadly Sins were dissolved and were relentlessly hunted by the Holy Knights.

Present day
King Liones, although realizing that a predicted Holy War would soon occur, ordered all the Holy Knights to lay down their weapons in an effort to avoid war. However, the Holy Knights, believing that the war was inevitable and that protection of the kingdom was their duty, captured the king a few days in a successful coup before Elizabeth found Meliodas, and began military preparations. The kingdom, now under the command of current Great Holy Knights, Hendricksen and Dreyfus, fell into a state of distress as citizens from towns and villages surrounding the kingdom were enslaved or forcefully recruited into joining the military effort: the men forcibly trained as soldiers, the women and children forced to amass food for storage, and the elderly forced to construct castle walls. Death has now become the penalty for insubordination under the rule of the Holy Knights, with them justifying their enslaving of the citizens with the fact that the war is being fought for their protection to begin with.

It is revealed that Hendricksen plotted to resurrect the long-sealed Demon Clan so there will be a formidable enemy for the Holy Knights to fight and win in the Holy War with aid from the New Generation Holy Knights.

Great Holy Knight
The Great Holy Knights are the most powerful of of the Holy Knights, and possess the authorities of commanding over them, thus making them the leaders of the Holy Knights. This gave the current Great Holy Knights, Dreyfus and Hendricksen, command over the whole country after the coup d'état.

Holy Knight
The Holy Knight is a title given to well established knights that have great strength, which is equal to that of an army. They have command over ordinary knights and train apprentices to become full fledged Holy Knights. All of them are imbued with extraordinary powers, such as Gilthunder's lightning abilities and Guila's explosion abilities.There are titles within the Holy Knight themselves, it seems the higher ranked they are the more power they have, these titles are:
 * 1) Cardinal
 * 2) Diamond
 * 3) Platinum

Apprentice Holy Knight
Apprentice Holy Knights, as their name suggests, are apprentices and disciples of existing Holy Knights who are undergoing training to become seasoned and qualified Holy Knights. They are fairly powerful compared to ordinary knights, whom they have authorities to command over, but are still much weaker than a Holy Knight.

New Generation
The Great Holy Knight Hendricksen has secretly been using the blood of a demon, which has power-enhancing qualities, to give new abilities to apprentice Holy Knights and other knights previously considered to be failures. The kingdom, not knowing the cause of many knights suddenly gaining great powers, has dubbed them the "New Generation". Jericho told Ban that the one who drinks the blood are known as "Reactors".

Old Generation
Before the creation of the New Generation, the Great Holy Knight Hendricksen had made another group of Holy Knight who are similar to the New Generation, however they were much more powerful than the New Generation and prove to be uncontrollable, turning into demons themselves.

Trivia

 * Holy Knight is a special job class in Final Fantasy Tactics for the PlayStation.
 * The practice of the current Holy Knights ingesting demon blood in order to enhance their powers is very similar to the Grey Wardens drinking Darkspawn blood in the RPG series Dragon Age.