The "Final boss" of normal mode, found in The Quarry. Killing it will activate the fake ending, while letting it perform "Reject Death" will enable Hardmode, and then the true game can begin.
Oh my god... Even in death we're a $%&@ing joke...
Bosch
What? How did you manage to die, that doesn't even make sense? We came all this way so I could watch you kill yourself in front of yourself, but not like this.
Bosch
If you are reading this, Talia and Nico are disappointed in you.
Lore
While initially thought to be Nowak's killer, and the reason he's stuck in Purgatory, he's actually Nowak's human form, having apparently jumped off into the quarry in an effort to kill himself.
Lore from the steam card "As he bleeds at the bottom of the quarry, he is truly, alone. His existence passes through not a single mind. His father, drowning in the warm depths of another bottle. His mother, long since adrift from existence, His brother, vanished either out of cruelty or tragedy. When they look for him, it will be far too late. To him, this place was a canvas, a respite from the uncaring universe above and below. To all others, this quarry is just that - cold stone cut for a cathedral long since constructed."
Trivia
Originally there was a 1% chance that the Corpse could be in a "Family Guy Death Pose" this got cut sadly[1]