Founding
Runeterra is both the spirit realm and the physical realm coexisting together. With the formation of Runeterra from the World Runes came the creation of the spirit realm with the physical realm. With this, the creation of all metaphysical aspects of existence were created. Thoughts, dreams, shadows, souls and, most importantly, spirits.
Spirits come in all shapes, sizes and power from malevolent demons to benevolent fae. With the later inclusion of mortals, spirit gods would begin to dominate the spaces of the physical realm and cement themselves as divine forces.
*Speculated content, subject to change.