Theories about why Kayle and Morgana are linked with Demacia
So my opinion is that they were originally Demacian citizens and they were both gifted magicians. Because of Demacia’s hatred of magic Kayle and Morgana self-exiled and took a boat to Shurima to live and study there with great magicians. Many years past and Kayle and Morgana showed potential for magic beyond any Shuriman for a long time. So they were chosen to take the ascension ritual but Morgana’s ritual went horribly wrong and she turned into an image of a fallen angel. The reason why they didn’t turn to animals is because they come from Demacia and Demacia has angelic aesthetics and this is what they consider as the most highest state.