Using this item on Black Hearts will activate the Black Heart's damaging effect.
Must use with two full Soul Hearts to work. One and a half will not work.
Converter's quality is treated as 2 for the purposes of Bag of Crafting.
Synergies
Book of Virtues: Spawns wisps in the middle ring, looking like hearts. Wisps have slightly higher health than average. Red Heart pickups can be used to restore their health.
Tainted Eden: Heart containers gained from Converter are kept, even after rerolling.
Black Judas / Tainted Judas: Converts one Black Heart into one Black Heart, keeping Judas’ health the same as before but activates The Necronomicon effect regardless.
Interactions
Bethany: Bethany cannot activate the Converter whether she has soul charges or not.
Tainted Bethany: When used while fully charged, adds 2 Blood Charges to her pool at no cost to her Heart total. When used with no charges, consumes 3 Blood Charges and produces 2, resulting in a net loss.
With Car Battery: Consumes 3 Blood Charges and produces 4, still at no cost to Heart total, resulting in infinite Blood Charges.
3DS The icon of Converter as seen on the lower 3DS screen.
Trivia
The Converter is a reference to a converter, a device or system that changes the form of something.
According to Edmund via the Four Souls Isaac lore stream, the Converter's sprite was originally supposed to be similar to an adapter that converted US-standard power plugs for UK-standard power outlets, then he "just threw some wires on it."[1]
The Converter can be seen as an opposite to Guppy's Paw. Where the Converter takes two Soul or Black Hearts to form a Heart container (or just one Soul or Black Heart as of Repentance), Guppy's Paw takes one Heart container to form three Soul Hearts. Additionally, their flavor texts are similar.
Converts two 
Soul Hearts or 
Black Hearts into one filled 
Red Heart container.
Converts one 
Converter's quality is treated as 2 for the purposes of 
Bag of Crafting.
Book of Virtues: Spawns wisps in the middle ring, looking like hearts. Wisps have slightly higher health than average. Red Heart pickups can be used to restore their health.
Book of Revelations / 
Satanic Bible: Allows for generation of Heart Containers. (
Schoolbag required)
9 Volt + 
Habit: Allows for an easy setup to get max health as long as one has a self-damage source, such as a 
Blood Donation Machine or a 
Devil Beggar.
Guppy's Paw:
Potato Peeler + 
Sharp Plug: Allows Isaac to generate infinite damage upgrades and 
Cube of Meat.
??? + 
Birthright: Removes one Soul Heart and grants two, effectively becoming a 3-room charge 
Tainted Eden: Heart containers gained from Converter are kept, even after rerolling.
Black Judas / 
Tainted Judas: Converts one Black Heart into one Black Heart, keeping Judas’ health the same as before but activates 
The Necronomicon effect regardless.
Bethany: Bethany cannot activate the Converter whether she has soul charges or not.
Car Battery:
No effect.
The Soul: Consumes Soul Hearts and produces 
Bone Hearts for 
The Forgotten. Does nothing when used by The Forgotten.
Tainted Bethany: When used while fully charged, adds 2 Blood Charges to her pool at no cost to her Heart total. When used with no charges, consumes 3 Blood Charges and produces 2, resulting in a net loss.
3DS The icon of Converter as seen on the lower 3DS screen.
The Binding of Isaac: Rebirth
