The admission process for the Repentant is conducted entirely in-character. If you wish to join the Repentant in service to the All-Father, contact Aztice Ethertone. Either a meeting can be arranged in-game, or you can write to me. You will need to tell me about yourself and why you wish to join.
Development of a detailed character history is encouraged but not required; if you have enough detail figured out to write a convincing letter, that is the only admission requirement.