A Soulshaped earns their names from the nature of their creation. When their soul was going to fuse with their body, it came into contact with the soul or energies of another powerful entity. This forever altered the nature of the soul, one that doesn’t suit the body the Soulshaped was born into, and so as they grow in power their body will change to better reflect the nature of their soul known as their True Soulform.
Now there are some rarer kinds of Soulshaped who are born normally, but afterwards have come into contact with a great magical outburst, undergone horrific experimentation, or suffered a powerful curse which has ended in the nature of the soul warping. This again will lead to their form changing to suit the soul’s new True Soulform.
Though it should be noted these same events have been found to also meet the conditions for awakening a sleeping Soulshaped’s soul, meaning it can be unclear if these events are true causes or more an unrelated event that revealed the changes already there.