Isaac's Heart

Isaac's Heart is a secret unlockable passive item.

Effect

 * Isaac's body becomes immune to all damage.
 * A heart familiar appears and closely follows Isaac. If the heart is hurt, Isaac is hurt.
 * Enemies now target the heart instead of Isaac. Eyes and other similar enemies, however, will still target Isaac.

Synergies

 * Aries - Isaac can cause contact damage without taking damage.
 * Blood Rights - Isaac can use Blood Rights infinitely without taking damage.
 * Breath Of Life - Isaac can be infinitely invulnerable, as invincibility carries out to the heart without hurting the player. Note that the item needs to be activated for longer than one second for the invulnerability to kick in, however.
 * Blank Card + XIV - Temperance - Isaac can use the Temperance card indefinitely to get infinite money.
 * Dry Baby - If Isaac's Heart is layered over Dry Baby, Dry Baby will block incoming shots and the heart will not be damaged by projectiles. Enemies touching the heart can still do damage.
 * E Coli - Isaac can turn enemies into poop without taking damage.
 * Gnawed Leaf - Invincibility carries over to the heart.
 * Holy Mantle - The shield effect carries over to the heart.
 * IV Bag - Isaac can use the bag without taking damage, effectively granting infinite money.
 * Kamikaze! - As long as the heart is away from the blast radius, no damage is taken. Character must be at high enough speed for this.
 * Midas' Touch - Isaac can turn enemies into coins on contact without taking damage.
 * Razor Blade - Isaac cannot take damage from the Razor Blade, allowing for infinite uses of the item.
 * The Nail - Demon Isaac can cause contact damage without taking damage.
 * The Virus - Isaac can poison enemies on contact without taking damage.

Interactions

 * Box Of Friends - Box of Friends does not duplicate the heart.
 * BFFS! - BFFS! will make the heart bigger, making it easier to get hit.
 * Sharp Plug - Sharp Plug can no longer be used.

Trivia

 * Isaac's Heart while it's following Isaac fittingly shares the same sprite as Child's Heart.
 * The nature of the item is similar to that of a Mask + Heart enemy.
 * This item is used in Challenge #30 (The Guardian).

Seeds
TPWZ 7CVR (Treasure Room below of spawn) PCJZ 03TG (Adjacent Treasure Room) W1TD 0BJN (Treasure room south of spawn)