Bosses
Bosses are very strong monsters found in 
Boss Rooms at the end of a floor.
Fiend Folio adds 27 bosses and 3 mini-bosses into The Binding of Isaac: Repentance.
This page is about Bosses added in Fiend Folio. More information about Bosses in general can be found in the vanilla page.
Bosses
Chapter 1
Chapter 1.5
Chapter 2
Chapter 3
Chapter 3.5
Chapter 4
Chapter 4.5
Mini-Bosses
Three new Mini-Bosses have been added to ruin your day! Psion has taken over 
Sheol to usurp Satan, and Gravedigger rises foes from the dead to help her conquer the 
Cathedral. Both of these Mini-Bosses will appear in their own Mini-Boss Room in their respective floors.
Additionally, if you have 
Risk's Reward, you can fight the Hermit!
Vanilla Boss Champions
Existing bosses within The Binding of Isaac: Repentance have also gotten some attention, as Fiend Folio includes 13 new champion variants, each with their own unique appearance.
Media
 Bosses 
| |
|---|---|
| Chapter 1 | Buck - Honeydrop - The Whispers - Griddle Horn - Buster - Meltdown |
| Chapter 1.5 | Ghostbuster - Cacamancer |
| Chapter 2 | Battie - Kingpin - Slinger - Monsoon - Aquagob |
| Chapter 3 | The Organization - Gutso the Great - Luncheon - Pollution - Tsar - Junkstrap |
| Chapter 3.5 | Warp Zone - Dusk - Madomme |
| Chapter 4 | Basco - The Sun - Peeping - Cacophobia |
| Chapter 4.5 | Mr. Dead |
| Minibosses | Psion - Gravedigger - Hermit |
| Vanilla Boss Champions | Golden Plum - Ghost Larry Jr. - Mucus Monstro - Technopin - Albino Widow - Beehive Fistula - Possessed Hollow - Wine Husk - Kidney of Infamy - Alien Loki - Fiend Mom - Alien Lokii - Grinch Krampus |