The earth just dose not fit in the psycotic definition of boxed insanity called Cathulu. The examination of the natural world, and there definitions don’t apply.
Its not that there a split personality, where they experience different realities, they just do not understand living people. As a necromancer, one of there earliest abilities is speaking to the dead. While I imagined this would be a one sided conversation, that was not the case. The ability to get an answer, was one of the bloodlines defining marks. The earliest stages of Necromancer have nothing to do with reanimation, or dark versions of common spell-craft. They get answers from the dead, as if they where posessed, in a trance, or prophetic dreams. That is risky for someone with the talent of magic.
The dead have little or nothing to say to the living. Nothing can change the choices they made in life, so the only resolution is from those rare mortal lives who see the invisiable. Some of these act like a guardian beast. They want a prince to judge there actions as either correct, or sympethetic. Any prince can only preform so many resurections. The risk being that they lose the ability to tell the living from the dead. Speaking to them is dangerous, if they attempt to possess the living. Normally, the living are not even seen by a spirit. They act out the repeating events in there former life. Still they can not answer what they did not know, but they can reveal any secrets they did know.