The Holy Knights 聖騎士 Seikish 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.

The Holy Knights are broken down into teams known as factions
Factions
Dragon Fang
Dawn Roar
Phoenix Fire
Snake Vemon

Ranks
Great Holy Knight
The Great Holy Knights are the most powerful of the Holy Knights, and possess the authorities of commanding over them, thus making them the leaders of the Holy Knights.

Cardinal
The Cardinal「枢機卿」 Holy Knights serve directly under the Great Holy Knights and act as their assistants. They may not necessarily be stronger than Diamond ranked Holy Knights, and some cardinals are elderly knights and wizards.

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.There are titles within the Holy Knight themselves, it seems the higher ranked they are, the more power they have, these titles are:

Diamond「金剛」-SS Rank
Platinum「白金」-S Rank
Sapphire「蒼玉」-A Rank
Ruby「紅玉」-B Rank
Emerald「翠玉 C Rank
Crystal「水晶」-D Rank
Apprentice Holy Knight-E Rank
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.

You can start out at Apprentice Holy Knight and work your way up, you may also challenge the next rank to get promotion, also keep it fair if you leave yourself open and the destroy you you must step down or work together.