At Mist Basin.
...
After brushing a bunch of branches aside, Link saw a black Mage Tower by the lake.
The Mage Tower of the Undead! That was the first thought that popped up in his mind.
Dark colors, strange stone carvings, black magic aura fluctuations – the features of the Mage Tower pointed to the identity of its owner.
The Necromancers – because they manipulated dead bodies and exploited souls, they were forsaken by the gods of the Light Pantheon.
If a Necromancer was originally born in the Realm of Light, once he devoted himself to the Dark Side and black magic, his soul would forever be forbidden to enter the Glorious Kingdom where the gods of the Light Pantheon resided.
A Necromancer's soul would wander forever in limbo and his life would continue indefinitely in this state. This was their state of immortality.