The Binding of Isaac: Rebirth — How to Unlock The Lost
Complete Repentance guide to unlocking The Lost character using the Missing Poster trinket and Sacrifice Room method. No more four-death puzzle required.
The Lost is one of The Binding of Isaac: Rebirth's most iconic secret characters — a spectral boy who dies in a single hit but accesses devil deals for free and eventually wields Holy Mantle for one free hit per room. In Repentance, the unlock method was simplified dramatically from the original Rebirth four-death sequence. You no longer need to die as Isaac, Magdalene, Judas, and Azazel in specific circumstances. The current method requires one trinket and one Sacrifice Room death.
Prerequisites Before You Start
- Unlock Missing Poster — Defeat The Lamb as Isaac in the Dark Room. You need The Negative from Satan deals to reach Dark Room consistently. This permanently adds Missing Poster to the trinket pool.
- Unseeded runs only — Seeded runs, daily challenges, and victory laps disable unlocks. Play normal or hard mode without a custom seed.
- Sacrifice Room access — Sacrifice Rooms appear randomly on any floor. You need a room with a spike tile in the center that damages you for half a heart per use.
- Do not use Ankh or revival items — Dying with Missing Poster in a Sacrifice Room unlocks The Lost. Accidental revivals as ??? or other characters waste the attempt.
Step-by-Step Unlock Method
Once Missing Poster is unlocked in your save file, start unseeded runs hunting for the trinket. Missing Poster has a 33% chance to reveal Super Secret Room locations and respawns you as The Lost on death outside Sacrifice Rooms after the character is unlocked. Mom's Box in shops helps — it spawns random trinkets when activated, increasing your odds of finding Missing Poster without waiting for natural trinket drops.
When you hold Missing Poster, prioritize finding a Sacrifice Room over everything else — even strong runs should be abandoned for the unlock if you find the trinket. Enter the Sacrifice Room and step on the center spikes until you die. The trinket consumes itself, The Lost unlocks immediately, and the "You unlocked The Lost" secret appears. After unlocking, Missing Poster still respawns you as The Lost on any death, making practice runs easier.
Tips for Finding Missing Poster Faster
| Strategy | Why It Works |
|---|---|
| Play as Azazel on Normal | Flight and short-range brimstone clear floors fast for more trinket rolls |
| Buy Mom's Box in shops | Guaranteed trinket spawn on activation — best Missing Poster farming tool |
| Check every trinket drop | Boss rooms, golden chests, and Ultra Secret rooms can drop trinkets |
| Use Greed Mode between attempts | Greed shops sell trinkets frequently for coin farming practice |
After unlocking The Lost, your next priority is Holy Mantle through normal completion marks — required before attempting Tainted Lost. See our character unlock guide for the full Lost → Tainted Lost chain and the Tainted Lost unlock guide for Home and Red Key requirements.
Frequently Asked Questions
Can I unlock The Lost in seeded runs?
No. Seeded runs disable all unlocks including characters, items, and secrets. Use unseeded normal or hard mode only.
Do I still need the old four-death method?
No. Repentance replaced the Rebirth method entirely. Missing Poster plus Sacrifice Room death is the only current unlock path.
What if I die outside a Sacrifice Room with Missing Poster?
Before unlocking The Lost, any death with Missing Poster does not unlock the character. After unlocking, you respawn as The Lost in the previous room.
Does Missing Poster work in challenges?
No. Missing Poster is unavailable during challenge runs per its item tag.
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