Military action
As is often the case when multiple religions exist in close proximity to one another, it wasn't long before violence broke out on Shardinia. The major religions all vied for dominance, vowing that theirs was the only God deserving of the devotion of the Shardinian people. The war would rage for hundreds of years, becoming increasingly bitter and costly.
The Elemental Lords were a notoriously quiet group of deities, rarely bestowing any guidance or counsel onto their followers, and when they did it was usually saved for only their most devoted and trusted clergy. They were mostly "hands off" too, choosing to oversee the lives of their flocks rather than interfere with them. However, there was one who was more loose lipped than the others, when it suited him to be so. Kossuth, The Firelord sought power - he wanted to prove that his faith, and fire, were superior to the faiths and elements of his peers. To do this, he planted a seed within the Church of Kossuth clergy - a seed that would grow quickly into a poisonous vine infesting almost all of Shardinia. Kossuth let one of his most faithful devotees in on a secret. In fact, as far as religions go, he let his devotee in on the secret. Kossuth told his follower of the existence of the afterlife. And of Celestia - where "good" souls go, and Infernus - where "bad" souls go. And he also felt is appropriate to tell a little white lie to generate the response he was looking for - that there was not enough space in Celestia for everyone on Shardinia. Only the most worthy religion would see its followers ascend to Celestia. Initially fought using primitive weaponry and early military tactics, the war saw extremely fast development in equipment and tactics, and more importantly the introduction to the world of magic.