Tulnas was a rather religious man at heart. As someone whose Direction was identified to be a talented mercenary with the capability to save many lives, he had no choice but to be exactly that.
In the wake of words that called him out to be someone great, he had worked extremely hard to become the embodiment of that set of words.
All this culminated into explaining his relationship with the Purity, or more specifically, the Priests in the Temple within Inhone City.
Because of his constant visits to the Temple after receiving his Direction, offering prayers as well as speaking with the Priests and Priestesses over a very long time, his relationship with the Temple became very solid.
He benefitted greatly from this relationship by getting access to large amounts of knowledge and some inside information on the Purity. He would also help as many times as he could to solve some issues that required his strength.