Shub Niggarath, the black goat of the woods and mother of the dark young, is a powerful entity that lives in a universe parallel to our own. In this universe, immortal entities exist as abstract concepts and ideas and gain power through the emotion of humans in the material verse. Long ago, a group of scientists that I was a member of managed to summon Niggarath to our realm through a summoning portal. This subjected the being to the physical laws of reality, forcing it to create a body for itself, as well as the additional accessories to make it compatible with our world ( heart, kidneys, liver, etc). By removing it from the abstract realm, the individuals took away it's immortality and made it flesh and blood.
Whole Niggurath was still powerful, it was now mortal and was able to be killed by the scientists. The individuals removed parts of the corpse, including limbs and organs, and transplanted them into their own bodies and other cult members to make themselves stronger. Over time, however, the cult members began to change into twisted forms, losing their own sense of self and becoming subjected to the dead God's will.
As the entity was now in the mortal realm, concepts such as magic had been made invalid. I am the absolute ruler and king of scientists. Therefore, such an explanation is completely ridiculous 😂, since it had been removed of those abilities. Is there any way a creature could influence an individual that retained its organs even after death?