Unlock Jacob & Esau in Repentance+

Ultra TL;DR route, mirror mechanic, and the Mines/Ashpit II chase for Knife Piece 2.

One Mother kill unlocks Jacob & Esau

Ultra TL;DR

Route at a glance

Basement/Cellar → Downpour/Dross I–II via the key door in the boss room.
Downpour/Dross II: Touch the white fire → become Lost-form → enter the mirror → pick up Knife Piece 1 in the mirrored Treasure Room. Exit the mirror to revert.
After the floor boss, open the bomb-boarded door (2 bombs) to Mines/Ashpit I.
Mines/Ashpit II: Press 3 yellow buttons → ride the minecart → pick up Knife Piece 2 → run the Mother’s Shadow chase back to the entrance.
Mausoleum/Gehenna I–II: Beat Mom on II → a red door appears → throw the knife to open Corpse I.
Corpse II: Drop down to fight Mother. Defeat Mother → Jacob & Esau unlocked

Achievements must be enabled: no seeds/dailies/challenges; mods/console must be off. Also, some unlocks require Hard mode. Check your run settings if things don’t unlock.

Step-by-step / Key details

Downpour/Dross II — The white fire & mirror (Knife Piece 1)

Find the white fire; touch it to become a ghostly Lost-form.
While ghosted, step into the mirror to enter a Mirrored World.
Grab Knife Piece 1 from the mirrored Treasure Room, then walk back through the mirror to return to the normal floor.
You revert to your original character after returning (and after room state updates). Touching the white fire again can put you back into Lost-form temporarily.

Mines/Ashpit II — Knife Piece 2 & the Mother’s Shadow chase

How to trigger the chase & get Knife Piece 2

You must already have Knife Piece 1.
On Mines/Ashpit II, find a room with a broken minecart track.
Step on three yellow buttons scattered around the room to “repair” the track.
Return to the track and ride the minecart through the sealed passage into a sub-area.
Pick up Knife Piece 2 — this immediately starts the Mother’s Shadow chase.

What the chase is like

Mother’s Shadow is invincible and slowly pursues you, occasionally screaming then dashing. Each hit deals 1 full heart.
Your items/consumables are disabled in the sub-area (innate flight still works).
Your goal: run back to the entrance you came from. Leaving ends the chase.
The return path spawns obstacles: timed spikes, poop, rocks shattered by environmental bombs, buttons, etc.

Survival tips

Don’t panic. Listen for the “Isaac!” cue — bait the dash from range, then sidestep.
Use door frames — transitions grant brief i-frames so you can shrug off a close call.
In tight hallways, pre-clear choke points or wait for the dash then slip past.
If you have flight, use it to skip spike patterns when possible.

Mausoleum/Gehenna II — Open the red door

After beating Mom on Mausoleum/Gehenna II, a red flesh door appears in the boss room. Fire or throw the assembled Knife at it to open the path to Corpse I. The knife is consumed when opening it.

Corpse II — Fight Mother

Drop into the hole in the boss room to reach Mother. Defeat her once with any character → Jacob & Esau unlocked.

Quick checklist / Before you start a run

Mods/console off; not a seeded/daily/challenge run.
Keep 1 key + 2 bombs for early alternate path access.
Plan for survivability during the Mines II chase (movement speed, flight if possible).

FAQ

Do I stay as The Lost after leaving the mirror?

No. You revert to your original form after exiting the mirror. Touching the white fire again toggles Lost-form temporarily.

Do I have to fight the mirrored boss?

No. It’s optional. Beating it grants a boss item, which is useful if your run is strong enough.

Which versions does this apply to?

This route is valid for both Repentance and Repentance+. The core triggers — white fire/mirror (KP1), Mines II buttons/cart (KP2), knife into red door, and defeating Mother — are the same.