Serina is apart of a sub race of elves that reside in heaven Serina race are blue elves cause their skin are blue. Blue elves need a male and female to have children even tho they immortal. They can have children with other race's if they choose , once it's another race, their bloodline and strength , abilities will be a mix of both races. Blue elves reside in the Heavenly city Uran which has a mine that produces endless resources for construction and other activities.