((This is the lore of the genes Life lines and life runes))
Life lines come from there close connection of being alive and dead at the same time. A Sylesti with the lines or runes can teleport and have some flight capabilities like a spirit. These Sylestis get the runes when they confront the twin gods of life and death and they chose to have them be there followers.
The twin gods live in the middle land of life and death and all beings of sylestia travel through there when they die but some get the life lines keeping them alive and dead.

I know this is short but it works. :D