Flashback Of Nammu's Back Story
It happened aeons ago when humans, magic, mage, sorcerers, vampires, and werewolves stayed in Pangea. Everyone had their own divided territory, the magicians, witches and wizards, being the most advanced technology-wise utilised their powers to their best.
They build houses, bridges, dams, fountains, irrigation to allow the flow of water for crops and supply water into houses. They build mud-brick houses, with lights for night time, a complex set of sanitation flow, with sewage being utilized as fuel for energy. However, they lacked in earth stones and gems, which was in abundance in the human world.
Contrary to popular beliefs, gems and stones do hold some magical powers of healing, finding love, maintaining general health and some other uses. So, the magicians would trick the humans into trading gemstones with them for use of low-level technological advancement.