Originally Posted by
Zeta Kai
Once per year, an Unsent must make a successful Will save or become Chaotic Evil. The Difficulty Class for this check equals the number of years spent as an Unsent divided by their Charisma bonus (minimum +1). Those that become Chaotic Evil immediately transform into fiends. A fiended undead is a creature with an equal Challenge Rating to the originals Unsent, but can be of nearly any type/subtype (no Construct, Fey, Giant, or Humanoid fiends have ever been reported, however). The specific creature is determined by the environment of where it was turned into a fiend; only fiends native to that environment will be created there (Cold subtype fiends created only in arctic areas, for instance).