could a malicious mind player be able to cause others to hallucinate, or make them go insane with fear and paranoia? what about a malicious heart player? slowly make everyone turn on each other?

Oooh yes, a Mind Player would totally be able to cast hallucinations, maybe a Witch or Heir, inducing a Change in their Minds? Maybe Rage could fit the bill for this too but I’m not sure. Heart has to do more with the inner character, one’s Soul, true being, so maybe Mind as well or even a Blood player would be better to turn everyone against each other.