It's not entirely known when it started exactly but legend tells of the guardians that protected the elders in times of war and strife. Their lives committed to their elders' cause, and would die a thousand deaths to protect them. The earliest of guardians were said to be protectors of the Great Sun Dragon God Helios. In this tradition they are clad in distinguished armor that takes on the appearance of polished gold (though not really gold), with symbols of who they swore to protect crested on their armor.
To be accepted any dragon blood race must join at a young age, training rigorously, and then after judgement and with success may they actually become a member. Members of the guard are strong willed and devout to their cause.
Ritual involves studying the history of dragons and the history of the Sacred Guard until they can recall from memory. Then if not already indoctrinated, must become a religious member that worships the Great Dragon God Helios. Next they are trained in the ways of fighting, and must show selflessness in the eyes of others. Once fully trained and of age, they must pick who of which elder to guard, it is then engraved permanently into their armor. The armor is magically 'infused' with the scale and flesh of the individual and remains a permanent part of their body not unlike some members of the Aegis who can also do this.