Complex sentence: He rules from the Hellish lands of Discordia and as his insanity worsens, he kills nearly everyone in his employ and even kills himself thus becoming undead and possibly immune to Roland's guns.
Split into simpler sentences: He rules from the lands of Discordia and, as his insanity worsens, he kills nearly everyone in his employ and even kills himself. He thus becomes undead and possibly immune to Roland's guns.