The Shadow is a Lovecraftian-like entity in the fictional universe of the Supernatural television series.
The Shadow is the oldest entity in the cosmos. Before God or even the Darkness existed, there was only absolute nothingness. This giant nothing is actually sentient, has a true form that even Angels would go mad from seeing, and its mindset is noticeably more alien than that of any other deity or cosmic entity. Similarly to Lovecraft's Azathoth, it is usually sleeping forever as a mindless entity.