The Echelon (エシェロン, Esheron) were spiritually aware beings who resided in the Soul Society before the First Shinigami-Arrancar War. Most prominent of their number is the creator of Reiseī, Shūshi Gensaku Kaenōra.
The Echelon first arose as the Three Great Families of Soul Society (尸魂界の三大した家族, Sourusosaeti no san taishita kazoku). Their members were comprised of clans who had exceptional spiritual abilities in vast numbers. The Kaenōra Clan reached out to the other clans, bringing them under one banner. During The Wandering Clans Era, the Echelon resided in more developed areas of the current Rukongai. They were primarily noble merchants, selling to nomads and selected clans in order to gain a profit. Their patriach's son, Shūshi Musokuno Kaenōra, perfected the art of Reiseī, allowing his people to unite as one culture and promote learning.
Their lives were mostly successful until Arrancar Elites began to terrorize their establishments and homes in the early days of the First Shinigami-Arrancar War. The Echelonians fought back bravely, but their greatest warriors were no match for these powerful Arrancars. They were nearly annihilated as a result of the conflict. One of their clans lost every one of their warriors and all of those who carried their knowledge and clan history. As a result, the clan leaders of the remaining two Echelon families signed a treaty with the Gotei 13 to cooperate in defeating the Hollows and Arrancars plaguing the Soul Society.
Influence in the First Shinigami-Arrancar War
The Echelon were taken in as loose allies of the Shinigami seeing as both were being attacked and killed by the Hollows. However, the members of the Echelon were not impressed by the way the Shinigami's way of handling their men, citing Hikaru Kurosaki and Seireitou Kawahiru as their primary targets of revulsion.
Fall of the Second House
Details of this information are limited. According to eyewitness records, the second house of the Echelon associated themselves with the Bakufu o Shinseikai. They became dissatisfied with the conditions they found themselves in, especially the lack of recognition gotten from the Gotei 13. Additionally, they also renounced Shūshi Gensaku Kaenōra as their leader thinking him a puppet of the Gotei 13.