Those afflicted by schizophrenia (a mental disorder) have delusions - most commonly, they hear voices and see hallucinations. If their delusions are strong enough, they’ll think their delusions are real, which will likely make them real. Delusions that angels or deities are speaking to them and telling them to do something, will cause them to do it (to potentially harmful effect). Their hallucinations may manifest as spirits. Delusions of persecution may cause actual persecutors (or even assassins) to appear from out of their imagination who then proceed to hunt them down and maybe even kill them. Even if they’re able to fight off their assassin, the very experience of having conjured one up will strengthen their faith that they will conjure up more or worse in the future - which in turn means that they will be randomly attacked by more, and more dangerous, assassins; so people who are visited by these experiences are called the deathmarked. These assassins often won’t be human, but will be spirits, and demons, and astral horrors, and other unimaginably terrible things, who are only out to get the schizophrenic. Suffice it to say that schizophrenics are rare. But because it is so abnormal, practically no one believes that people can be born as natural schizophrenics, and so there are no natural schizophrenics. Instead, its onset is usually caused by mages with malicious intentions, causing this disorder on their victims in an attempt to make them self-destruct.