
It's a little spider familiar that wedges itself into Isaac's face, with its legs poking out of his eye sockets.

In the versus screen, The Witness's boss portrait has it looming over Isaac, instead of the "facing Isaac from the side" view of every single other boss.It's implied to be an undead Mama Grudy that witnessed Isaac killing his mother. The Final Boss of the Corpse, The Witness.It really puts the Scarred Womb to shame. Doubles as Nausea Fuel, even by this game's standards. And let's not even get started on the music that plays, which feels like something out of a Creepypasta. As a result, the entire level is dead and rotting, and is teeming with enemies that are either rotting away (with visible skeletons) or feasting on the decaying meat. It's the Womb chapter, but after the destruction of Mom's heart. Once you hear this music, you have no choice but to get into the new floor, Corpse.It's almost as if the game is telling you "you've made a horrible, horrible mistake" not completely unfounded, since you just killed your mother, and this is a grave reminder that she's dead. It sounds like Lavender Town, HILL Act 1, and the Reverse Song of Healing all rolled into one.

The music that plays after killing Mom's Heart in the Mausoleum, " Spinning Intensifies ".
