The Dark One

The Dark One is not just one person but instead many. The darkness is a magical entity created by the dark god. This darkness needs a host though. The Dark One whoever it may be is extremely powerful, with power close to that of a god, however even they can't break the core laws of magick. The Dark One is also immortal, they can not die of age, weapon or poison. However they can still die in a sense. The Dark One is bound to a ring. If someone where to obtain the ring and put it on the Dark One would die, and whoever put the ring on would then become the new dark one. The dark one can keep their powers without the ring on but once it is worn by another the trade is made. This is how the darkness has persisted for so long.
Attempts have been made to permanently stop the Dark One, some have even succeeded. The Dark One has been sealed away twice, both times a different Dark One. Yet both times the power lust of mortals have lead to the Dark One's freeing. It seems that this evil can never be truly stopped, bound to corrupt the good and feed the terrible for all of time.
The Dark One has been feared in all cultures for all it's time, not even the dragons meddle with the Dark One's affairs. In Tir Orail, The Vale and the Eldre mountains the summoning or conspiring of or with the Dark One is illegal and it punishable by death.