The ring of of change was created in an age before humans when elves and dwarves ruled to gain ultimate power they needed to create something to change themselves so the elves and the dwarves put their differences aside to make the ring of change the dwarves used their hell-forge a forge of ultimate heat the only thing that could melt and mould minotheum the most powerful ore in the land. After the dwarves created the ring they put a zelcho crystal in it.
The elves took the ring and enchanted it in the sky temple where it was blessed and granted the power to transform any creature into whatever they desired but the elves and dwarves fought over the ring and after thousands of people had died the ring was lost for eons the ring has been lost but it is time for it to awaken again.
Though the ring survived it was damaged not physically but the spell was damaged and so instead of being able to choose how you change it is completely random but one things for sure once somebody puts on the ring they will never be the same again.
The ring is calling for somebody to wear it you, you adventure to the ancient ruins and without realizing it finds the ring and puts it on.