The Shadow Prince

A rumor can become so vivid and so persistent that it comes to life, creating a brainchild-a living illusion that hatches from an intense belief in a remorseless and implacable killer. Often, these rumors swirl around the victims of a @UUID[Compendium.pf2e.spells-srd.Item.Phantasmal Killer] spell. A brainchild's capabilities grow when they pursue a believer but deflate against skeptics, making them only as bad as one thinks they are. A simple drive to stalk, terrify, and kill propels a brainchild, but the creature might also exhibit other behaviors ascribed to them through gossip.