A Jina is the rank a Wan Kuei attains after spending some time as a disciple. Normally this happens at the end of one's koa, where a disciple finally experiences the state of ling after living the tenets of their chosen Dharma.
When this happens, their minds and body open to a greater degree of power and magic. This flash of enlightment, the first understanding of their potential and the ways to control it, is a major accomplishment for a disciple.
Becoming a jina is a profound event among the Wan Kuei, as this brings additional social status and responsibilities. At this point many are assigned their own disciples to train, to ensure the future of the Court and its ideals.
Jina are Kuei-jin who managed to attain ranks 4 to 5 in their Dharma. This is normally the point where characters gradually cease becoming wandering troubleshooters for a Court, and will have to play the political game, if only to avoid having the local Mandarin on your case for insubordination.