Lichdom

One of the few categories of true undeath still present in the world after the creation of The Treaty of the Dead. Khydar the Unnatural has far less control over these conditions and those affected by them, although their related nature gives him a modicum of influence.
Lichdom is achieved by spellcasters seeking to avoid death. They perform a ritual to rip their own souls from their body at the point of death, sealing it inside an object of their choice. They must regularly feed their captured soul with the souls of others, making liches rather unpopular with both Astus and Khydar as they consume souls so that neither god can claim them.
If a lich's body is destroyed, but their soul survives, their body will reform after a short period of time, allowing them to continue their schemes.