After defeating the boss in Corpse 2, The Binding of Isaac: Repentance players will receive indication that a Strange Door has appeared in the Depths. As is the case with many of the doors in this roguelike, the Depths door is locked initially, and fans will need a particular item to get through it. Detailing how to get the relevant item is the precise purpose of this guide, and it will also describe what players will find past the Depths door in The Binding of Isaac: Repentance.
To get right to it, fans that wish to pass through the Strange Door must use either The Polaroid or The Negative that is obtained by defeating Mom. Notably, The Binding of Isaac players will need to use The Fool card to teleport after they have collected one of these two items, and one can be obtained by blowing up a marked skull that always spawns in Depths 2. Alternatively, fans can enlist Azazel's help here if that is their preference, as he always starts with The Fool card.
After using The Polaroid or The Negative to unlock the Depths door, players should enter the newly-accessible room and fall into the hole that they find there. Roguelike fans will now need to make their way back through the floors that they cleared previously, and those that do will ultimately encounter a beam of light. This beam leads to The Binding of Isaac: Repentance's final new floor, and players that wish to avoid spoilers are advised to stop reading now.
With that said, fans should now find themselves in Home, where there are a number of rooms to explore. One of those rooms is Mom's, and opening the chest that is found within it will unlock the Red Key. Players can also look at Mom's bed to be transported to an alternate version of Home, and interacting with the television in the nearby room will initiate a battle with Dogma, a new boss in The Binding of Isaac: Repentance.
Fans that defeat this enemy will then be thrown into one more battle, and indeed it is the final boss fight in this new The Binding of Isaac DLC. Considering the high difficulty level of this battle, players should not be extremely surprised if they do not come out victorious on their first time through. However, fans that are interested in seeing the true ending should not give up, as it is right around the corner.
The Binding of Isaac is available on PC, Nintendo Switch, PlayStation 4, and Xbox One.