Irminsulism is the religion of the Nullhi people.
According to Nullhi Mythology, the universe was created by a being known as “Tellus“ The world Tellus created was a barren and desolate rock, because of this, Tellus planted a single enchanted seed into the ground. From this seed grew a great tree that would go on to spread and grow life all throughout the world, every living creature could trace its genealogy back to this tree, which was since called “Ermeinsalei”. Once the world was full of life, Tellus shared a portion of their wisdom with all the different humanoid species throughout the world, making them self-aware and giving them a conscience. After this Tellus removed themself from worldly affairs permanently, and was never seen or heard from again.
One of the humanoid species given wisdom by Tellus were the Nullhi. For centuries after they were given wisdom, they fought countless wars amongst one another, until eventually their fighting led to the destruction of Ermeinsalei, completely severing any remaining connection between our world and Tellus.