The Church of Sunlight's hatred of the undead went back thousands of years to the early years of the Chaos Era.
After molding the Earthly Plane, the Great Gods gave birth to the Nine Earthly Guardians to protect mortal beings while they remained in Etlan, the Celestial realm.
Of the Nine Guardians, the Three Colossuses of the Cosmos had been created by Satrris, the goddess of darkness, moons, and night; and by Solaeris, the god of light, sun, and day.
During the Second Age (also known as the Golden era) Solaeris had sometimes descended to the Earthly Plane in various guises and forms. This to interact with mortals and with the Earthly Guardians.
So it was that, over time, Solaeris had ceased to see the Colossuses as mere creations of his own and began to treat them more as a father would treat his children.
