These ex-Sentients used to be regular people, but used magic so recklessly in their life that, upon their death, the magic left contained in their bodies took control of their corpses and now runs wild in the world, finding and consuming new sources of magic to keep themselves together. They retain very little of their previous selves, though some have been shown to recall important memories from their past life and, if observed from afar and thinking they are along, they may be spotted playing with the environment around them. They are one of the few undead who do not appear undead; they often look as if they were alive and healthy people.
Though corrupted spell-casters are considered dangerous they are very rarely deadly, especially to non-magic users. Their status as dangerous comes from their need to feed on magic; if they come an individual who uses magic, they will hunt them down and drain the magic from the user’s body and, alongside it, much of their health and life-force. The drained becomes sickly and weak for a long time after facing a corrupted spell-caster, sometimes taking a few years to get their energy back, and some never fully recover their magical abilities after an attack.
In the 6,300s, the Kuturian library paid for the capture and safe delivery of 53 corrupted spell-casters, of whom they tried to communicate with. Sadly, experiments proved that corrupted spell-casters were in no way sapient or intelligent and were simply a corpse possessed by extreme amounts of living magic. The 53 spell-casters were kept in confinement for roughly 30 years, with attempts made the entire time to communicate with them, until their bodies grew old and they eventually all passed away.