The Binding of Isaac Repentance+: how to unlock the 17 Tainted characters (Red Key, Home)

Repentance added 17 tainted versions of Isaac's characters, and the game never explains anywhere how to unlock them. Yet there's only one method: reach the Home floor, open the hidden closet in the hallway leading to Mom's Room, and touch the crying baby inside. This baby is the tainted version of the character you're currently playing. One unlock per run, so seventeen runs at minimum.

The good news is that the route is entirely scripted: once understood, it repeats identically every time. The bad news is that the Red Key, which opens this closet, is only guaranteed once — on your very first visit to the Home. From the second tainted character onward, you have to bring your own key, and that's precisely where most players get stuck.

Here's the complete protocol, from the Strange Door in Depths II to the closet, with the details that most French-language guides leave out: the Marked Skull, converting trinkets into Broken Keys, and the special case of Eden.

The two prerequisites before starting any run

The first is unavoidable: you must have defeated Mom at least once, at the very end of Womb II. It's this victory that makes "A Strange Door" appear, and nothing else unlocks it. If Mom hasn't fallen yet, you'll first need to complete the full alternate path — Chutes, Mines, Mausoleum, Womb — with both knife pieces.

The second is an item: The Polaroid or The Negative, which Mom drops in her boss room in Depths II once unlocked. The door consumes them upon opening, unlike the Vault entrance, which leaves the item in your inventory. The Bloody Polaroid, the Broken Ankh, the Cracked Orb, Cain's Other Soul, and the Sharp Key also work; Dad's Key, however, does not.

A routing point that's often misunderstood: the door appears in the starting room of Depths II and its variants, Necropolis II and Dank Depths II. It never appears on the alternate path. For an unlock run, you should therefore descend via the classic route, without touching the Chutes.

The Marked Skull, the key to backtracking

There's a design trap in this sequence. The Polaroid drops in Mom's boss room, and the only exit from that room is the trapdoor leading down to the Womb. But the Strange Door, on the other hand, is located all the way at the top of the floor, in the starting room. So you need to go back up without taking the trapdoor.

The reliable solution comes down to one piece of scenery: a Marked Skull always spawns somewhere on the chapter's second floor. Destroying it always drops a guaranteed 0 - The Fool card, which teleports you to the starting room. Spot it and leave it intact before going to face Mom: it's your ticket back. Failing that, the Ventricle Razor, a Tranquilizer Pill, or any teleport effect serve the same purpose.

One last thing to check before leaving: if the run's timer is still under twenty minutes, the Boss Rush is accessible on this floor. The item is free and the detour only costs two minutes.

The Ascent: what changes compared to a normal descent

The door leads to a special version of Mausoleum II — Gehenna II depending on the variant — where the boss room contains no boss, only Dad's Note. Picking it up triggers the Ascent.

The principle is the same as the Backwards challenge: you climb back up through shortened versions of every floor you've already been through, starting each time in the boss room, with the beam of light leading to the floor above located in the original starting room. A few rules to know:

• Treasure Rooms and Boss Rooms remain in the state you left them in. Other special rooms don't appear, with the exception of red rooms.
• Monsters are stronger versions of those from the original chapter, with variants that don't exist anywhere else in the game.
• From the release of Mausoleum II onward, every hit taken costs a full heart, exactly as in the Womb or the Corpse. An Ascent begun with a heart and a half rarely ends well.
• Treasure Rooms you skipped stay locked, but their contents are regenerated: keep two or three keys in your pocket.
• The Basement I beam of light leads to the Home.

This last rule opens up an optimization known to high-level players: deliberately skipping the first Treasure Rooms increases the odds of a Planetarium appearing, and any missed items are still recovered on the way back up.

Inside the Home: exactly where the closet is

The Home has a fixed layout, identical on every visit: Isaac's bedroom (with a bed and a golden chest), a hallway, a small room containing a pickup, the living room, a second hallway, then Mom's bedroom. Sleeping in Isaac's bed heals you, or grants three soul hearts if you have no red heart containers.

The chest in Mom's bedroom contains the Red Key the first time it's opened, which unlocks the item permanently. On subsequent visits, this chest draws from its own pool of Mom-related items: the Red Key can still come out of it, but it's rare. Don't count on it.

The closet opens by using the Red Key, a Broken Key, or Cain's Eye against the left-hand wall of the hallway leading to Mom's bedroom. When you're holding one of these keys, a barely visible red outline reveals the location of the door. Inside, the Tainted version of your character lies on the floor crying: touching it is enough, the unlock is immediate and permanent.

Three practical consequences that many people are unaware of:

• Neither Dogma nor The Beast are necessary. Once the baby is touched, you can quit the run right away: the character is unlocked.
• Only one unlock per run. Switching characters along the way — dying with the Wanted Poster and coming back as The Lost, for example — doesn't change the baby in the closet, which remains that of the first character.
• In true co-op, the closet contains only player 1's Tainted character. If you're chaining unlocks with multiple people, you need to alternate who holds the first controller.

If the Tainted version of the character being played is already unlocked, or if you're already playing a Tainted character, the closet contains the Inner Child instead.

The workaround for the Red Key problem: trinkets

This is the mechanic that makes the following sixteen runs manageable. During the Ascent, every trinket left on the floor in a Treasure Room or Boss Room turns into a Broken Key. A Broken Key opens the closet exactly like the Red Key.

The routine to adopt, right from the start of the descent: every time you pick up a trinket you don't want, go drop it off in the Treasure Room or the Boss Room of the floor rather than tossing it just anywhere. Two dropped trinkets are enough to secure the way back up. The Forget Me Now, which copies pickups from one floor to another, lets you accumulate even more.

The other sources of keys are more random: the Red Key can appear in a Curse Room, and Pandora's Box used directly at the Home can produce it.

Chaining the 17 runs without spending the whole week on it

Start with a comfortable character — Judas or Azazel do the job — to pocket the Red Key on the first visit. Save the fragile ones for last, once you know the route by heart: The Lost and The Keeper handle the Ascent's full-heart rule very poorly, and Holy Mantle becomes an absolute priority in the Treasure Room.

Eden's case deserves separate treatment. Every run started with him consumes a token, and tokens can only be obtained by defeating Mom's Heart, It Lives, Ultra Greed, or The Beast. For Tainted Eden, then, don't quit the run after touching the baby: chain straight into Dogma and then The Beast, and you'll get the spent token back.

Finally, a curiosity that can save an entire run: using the Glowing Hour Glass in the starting room of the first floor, without having entered any other room, sends you straight to the Home. This case is rare since you need to start the run with the item, but it's exactly the kind of draw Eden can offer.

The official French names of the 17 Tainted characters

The French client translates character names, which complicates reading English-language guides. Here is the correspondence, as it appears in the game:

And after unlocking

The Tainted characters aren't selected from the usual list: from the character selection screen, you need to press E on keyboard or RB / R1 on controller to switch to the damaged menu reserved for them. Each has seven achievements instead of the fifteen of a regular character, which makes individual completion noticeably shorter than it looks.

One last piece of methodological advice: treat each unlock run as a race, not as a progression run. You don't need to finish the game, nor to survive after the closet. A tainted character touched is a tainted character earned, even if you die to Dogma the very next minute.