A Strange Door
A Strange Door is a special exit that is unlocked by beating 
Mother for the first time. It leads to a special version of 
Mausoleum/
Gehenna II, which contains 
Dad's Note, which starts the Ascent, and eventually 
Home and the fight against 
Dogma and 
The Beast.
The door spawns in the starting room of 
Depths/
Necropolis/
Dank Depths II. It can be opened by giving it 
The Polaroid or 
The Negative. This can be done through methods such as using a teleportation card, a Telepills, a teleport activated item, 
Ventricle Razor, or 
Forget Me Now after defeating 
Mom, escaping the boss room. The door can also be opened with 
Broken Padlock, 
Cracked Orb, 
Faded Polaroid, 
Soul of Cain, or 
Sharp Key, but not 
Mr. ME!, 
Dad's Key,
Mysterious Paper, or a 
Get out of Jail Free Card.
Having more than one of The Polaroid or The Negative, (such as through 
Diplopia or 
R Key) will only remove one to open the door. Faded Polaroid is always taken first if held, then The Negative and then The Polaroid.
A Marked Skull always spawns somewhere in the second floor of the chapter. Destroying it will drop a guaranteed 
0 - The Fool (or a Telepills if holding 
Little Baggy), giving a reliable way to open the door. It is recommended to visit the 
Boss Rush room for a free item before teleporting out if possible. The Telepills will become a ??? if Isaac has Little Baggy and 
False PHD, rendering it more difficult to exit the boss room.
