[more info]:

its real form it's like a very pale black haired woman with no eyes and blood coming out his mouth, it floats and has the half of the body torn off and a long spine, its real name is Aberratiora.

It was summoned by a group of satanists and spreaded via cursed cartridges back in the 90s when Sonic was extremely popular. Now, it's spreaded via executable files, CDs, viruses, videos, webpages or in the deep web.

The things the game or video can cause to the "victim" are normaly seizures, insomnia, heavy nightmares, or in the worsts cases, sleep paralysis, huge brain damage, self destructive thoughts and activities, kys or heart attacks after the game ends. Many "survivors" said that the hedgehog screamed and broke the tv, a pale woman appeared in their room, in the end showed graphic images, etc..., but no one knows what exactly happened there.