Edmund McMillen's indie classic The Binding Of Isaac is one absolutely stuffed with secrets, rare encounters, and difficult achievements that unlock exclusive content. The Binding Of Isaac: Repentance is the final DLC pack for the game and features a whole host of new secrets and chance occurrences that only the most dedicated players will experience.
The DLC changes a lot about how The Binding of Isaac is played, including hundreds of new items and interactions – interesting, many items are directly tied to secrets. The Red Key, for example, unlocks some major permanent upgrades in the later stages of a Repentance run, while other secrets can only be found by actively avoiding certain in-game encounters.
6 The Planetarium
When one looks at the spawn rate of the Planetarium, it seems nearly impossible to access. It has a base one percent chance to appear that also requires the player to have found three astrology-related items on their run. This requirement doesn't follow Isaac across playthroughs, they must be picked up without dying. The room does, however, gain a 20 percent bump in the chance to spawn if the player skips Item Rooms.
The player cannot go into an Item Room for it to count as skipped – they have to avoid it completely. When the player has skipped five item rooms total in a run, it's guaranteed to appear. Keep in mind, though, that the Planetarium requires a key to enter just like any Treasure Room in later stages of a run. The items in the Planetarium are spectacularly good. All 11 new items are related to the planets, the sun, and the moon in our Solar System, and give Isaac huge benefits when picked up.
5 Unlocking Jacob and Esau, and Bethany
Each DLC for The Binding of Isaac has introduced new playable characters. The Binding of Isaac: Rebirth introduced Azazel, Lazarus, Eden, and The Lost, while The Binding Of Isaac: Afterbirth and Afterbirth+ introduced Lilith and Keeper, and The Binding of Isaac: Repentance introduces Bethany and Jacob and Esau as a two-in-one character.
The requirements to unlock Bethany and Jacob and Esau are really tough to reach. To unlock Jacob and Esau, the player must kill The Witness. It's easier said than done, though, as The Witness is perhaps one of the hardest bosses in the entire game, and that's really saying something. To unlock Bethany, the player must defeat Mom's Heart or It Lives! as Lazarus, without losing a life in the whole run on hard mode – good luck!
4 Downpour, Mines, Mausoleum, and Corpse
The Binding Of Isaac: Repentance brings four new zones to the game – Mines, Downpour, Mausoleum, and Corpse. Each area is home to new enemies and new paths through the catacombs of Isaac's basement, as well as new bosses and unique encounters. However, these areas are not unlocked automatically upon downloading Repentance: they must be unlocked by defeating Hush three times.
The achievement A Secret Exit was added in Repentance, and it must be earned for the player to have a chance at finding these locations. Once unlocked, each area has a unique entry requirement. To access Downpour, the player needs to use a key on the locked entrance at the end of the first chapter, To access Mines, you must bomb the exit of the second chapter (Caves/Catacombs). To access Mausoleum, Isaac must sacrifice two hearts worth of health at the end of Depths or Mines. To access Corpse, Isaac must defeat Mom in the Mausoleum, open the red door with both Key Pieces, and then defeat Mom's Heart which will spawn an entrance to Corpse.
3 Tainted Characters
Tainted characters are a new system introduced in Repentance that inherently changes how each of the main characters behaves in-game. There is a tainted version of each playable character – that's right, all 17 of them – making for a total of 34 playable characters all with their own unique differences to their original form. Tainted Cain, for example, starts with the Bag of Crafting that lets him craft any item from those present around him.
Each Tainted character is unlocked the same way, but it's not an easy task. The player must find a Red Key in their run and make it all the way to the new final chapter, in the new final area: Home. When in Home, the player might see red outlines on the walls. When the Red Key is used near these outlines, a new secret room will appear offering some items to the player. The Tainted character unlocked each time is the same as the one you are playing as – so it will take 17 full runs to unlock each one.
2 The Mirrored World
The Mirrored World in Repentance eluded fans for a short time before they figured out how it works and exactly what it does. On the new levels Downpour and its alternative version Dross, there will be a white campfire that spawns somewhere on the level. It doesn't damage the player, instead, it turns Isaac into the Lost. Somewhere else on the floor there will be a mirror that will take Isaac to the Mirrored World when touched (as long as he is transformed into The Lost).
The Mirrored World is a, well, mirror of the current floor but without the chance of spawning a trap door upon defeating the boss. It doesn't mirror destroyed objects and slain enemies, though, so you will have to go through the floor again. When the boss is defeated it will drop Knife Piece 1 instead of normal loot. This spawns Knife Piece 2 on the Mines or Ashpit floor and lets Isaac get out of the mirror and back into the real world.
1 The True Ending To The Binding of Isaac
Repentance is the official final expansion for the beloved indie classic. It's been a long road for Edmund McMillen and the development team throughout the years, but even the best chapters have to come to an end. The final (and official) ending for Isaac's biblical story is presented at the very end of the expansion.
Without spoiling it, this final scene is unlocked by defeating Dogma and then The Beast, the "real" final boss of the game. The Beast is based on the very first beast described in the Book of Revelations and seeing as how The Binding of Isaac is not-so-secretly about the cruelty of religion in general, the real ending is a fitting wrap on the blasphemous tale as a whole.