After defeating Mom in Mausoleum 2 or Gehenna 2, The Binding of Isaac: Repentance players will encounter a strange red door. As many fans are sure to expect, getting through this door requires the use of a particular item, though exactly what is needed may not be obvious. Shining some light on this matter is the precise purpose of this guide, and players that read on will have all of the information that they need to unlock the red door in The Binding of Isaac: Repentance.
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To put things simply, players that wish to pass through the red door must first assemble the Knife. To do this, fans must collect two Knife Pieces, which are accessed from Downpour/Dross 2 and Mines/Ashpit 2. While some The Binding of Isaac players will undoubtedly already know how to obtain these two items, those that do not can find full details in the following paragraphs.
Updated September 5th, 2021 by Russ Boswell: The Binding of Isaac is now bigger than ever. With the release of Repentance, players have even more areas to explore and new items to unlock. Even better, there is more lore to uncover concerning the unfortunate Isaac, with new endings to see. To get some of these endings, and unlock new areas, players will need to get their hands on some specific items. The Binding of Isaac Red Door is one of the key components to getting the ball rolling towards the "true endgame." In order to better help educate new players on this Isaac Red Door, the following guide has been updated, with more information and a section outlining just what players can expect when opening the Red Door in The Binding of Isaac: Repentance.
Where To Find Knife Piece 1
With respect to Knife Piece 1 in The Binding of Isaac: Repentance, fans can find it in an item room past the mirror that appears in Downpour 2 and Dross 2. To get through this mirror, players need to locate a blue-grey flame on the floor and then walk into it to be transformed into the Lost. Notably, navigating through the area that is beyond the mirror can be a bit challenging, and fans should act with care as they make their way to the first Knife Piece.
Where To Find Knife Piece 2
Next up is Knife Piece 2 in The Binding of Isaac: Repentance, and it can only be collected if a player already has the first piece in hand. If a fan has met this prerequisite, then they should look for and press the three yellow buttons that appear in Mines 2 and Ashpit 2. After hitting all of these switches, players will be able to jump into a minecart on the floor and access the area with the second Knife Piece, and a deadly chase sequence will begin when the item is picked up.
At this point, roguelike fans will have the completed Knife, and they should throw it at the red door in Mausoleum/Gehenna 2 in order to open it. Indeed, players will now be free to pass through the previously-blocked portal, though it important to mention that a boss fight awaits on the other side. Once this foe has been dispatched, fans will gain access to the Corpse floor, and clearing it will cause another door, which is opened in a very different way, to appear in Depths 2.
WARNING: THE FOLLOWING ARE SPOILERS FOR THE BINDING OF ISAAC: REPENTANCE.
What Can Players Expect In Corpse?
Those that collect the knife and manage to slash open the red door will find themselves in a new area known as Corpse. This dark labyrinth is filled with dreary imagery and is filled to the brim with a wide array of dangerous enemies all themed around the concepts of death. It can be quite challenging the first few times players find themselves here, and learning each enemy's attack patterns and behaviors is key to successfully navigating the grotesque area.
The main attraction in this area is the final boss of the level, which will always be Mother. This ghoulish-looking boss is incredibly difficult for the uninitiated and stands with a staggering 4222 health. She can quickly end a variety of characters with her powerful attacks. She features two forms (a second which triggers when she has 2222 HP left), with the second moving faster and pursuing players with more attacks.
Defeating Mother will unlock Ending 21, and an additional door and set players on a path towards gaining the final ending in The Binding of Isaac.
The Binding of Isaac is available on PC, Nintendo Switch, PlayStation 4, and Xbox One.
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