The game has at least 4 in game religions. These religions actually have mechanics that support them in game. It wont be possible to make a player made religion that is supported by mechanics. Its possible to make an RP cult/religion, but nothing supported by the game itself.
Lo, there do I see my father. Lo, there do I see my mother, and my sisters, and my brothers. Lo, there do I see the line of my people... Back to the beginning. Lo, they do call to me. They bid me take my place among them. In the halls of Valhalla Where the brave may live forever.