The Silver Crane is a goodly discipline and may only be learned and used by those who have a good alignment who is channeling a good aligned outsider (such as an Argent Oracle). It focuses on strong strikes designed to combat evil, defensive abilities to protect those in need, and celestial insight to combat foes. Students of the Silver Crane rely on the oracular abilities of their celestial patron to guide their abilities and bring them safely through battle by seeing danger before it happens and anticipating the movements of their foes.
After the fall of empires and nations, the destruction of academies and temples due to war, martial adepts who trained in these places went their separate ways to form enclaves of their own, practicing their arts how they saw fit. Some founded religious orders, some created new temples and academies, some formed secret societies, some simply passed their training down to a single apprentice and urged them to do the same. In modern times, with a new renaissance of martial prowess on the move, a resurgence of less than wholesome disciplines, long forgotten, have resurfaced in the world. There are those who seek to share their souls with demonic entities for power who utilize the dark arts of the Black Heron. However, in this age of renaissance, the goodly races have a new art to combat the horrors given to them by an enigmatic group of incorporeal celestials that refer to themselves as the Argent Oracles. As they have no forms of their own, they grant their martial prowess to those who are willing to channel their essence in combat, learning their martial discipline known as the Silver Crane.
Any and all are open to learn this discipline, assuming that they have somehow called the attention of one of the Argent Oracles and have begun to channel one of their essences through their soul and form. Additionally, it's possible that other martial celestials may have picked up this trick (such as Solars and Ghaeles) and have made themselves available to mortals willing to fight in their name.