Press the flag. The final (and only) boss of the game, The Taker. I could've drawn his final form, but I personally like his floating head form more. If you stand still for too long, he will show up, take you, and then just spam the screen with "TO TAKE THE DEAD" over and over again. This guy is great. A fitting final fight for the main game. The inspiration for him is SO messed up though. Just the inspiration ALONE makes him the scariest creature in the game. It's so messed up, I don't even want to say it, and I insist you avoid it.
Spooky's Jumpscare Mansion TAKEN TAKEN TAKEN TAKEN