Branch of the Witch King

In a split second, Talin had seemingly transformed from the Witch King into a monster that had crawled out from the depths of death. A blood-curdling undead, decaying yet powerful. 

Since curses weren't effective, he had chosen to use Art of the Undying to increase his close-quarter combat abilities.

Once he turns into this undying form, his physique toughens and his vitality becomes unfathomable. He no longer fears normal attacks and gains enormous strength and ridiculous speed. His body also contains a potent poison. Ghosts and gods begin following him. 

The only shortcoming of this evil art is that it has after-effects, even if deactivated in time. The user's body become like a corpse, his status near death. If he uses it too many times, surpassing the limits, his vitality will gradually disperse and his flesh will decay. Around twenty days later, he will die an agonizing death.