Undying Heart

Info
Undying Heart is another top tier heart. Although it only has 10 HP (half of Lesser Heart), it revives if it dies after every room.

Strategies
This heart should always be placed at the rightmost slot, always granting your next rightmost heart a 10 hp cushion before it starts taking damage. It can be used effectively with Adrenaline, as there is no risk of losing the heart after taking its hp below 50%. There is basically no situation where you ever need to swap out this heart, as long as you put it on the rightmost slot your run should be a lot easier.

Trivia

 * Undying Heart is the only heart that cannot be destroyed in the entire run
 * Losing this heart still plays the heart loss animation
 * There was a bug in earlier demos which granted invincibility when undying heart was used with body bag hearts
 * This is technically the weakest heart in terms of HP in the game