7 Health management or why having 1 HP is near-optimal

New TBoI players, as mentioned above, tend to overrate HP, prioritizing it above other more important stats.16 Newbie TBoI players might be wondering about the title of this section and why I believe it to be so (along with many other more skilled players).

In short, you can apply the Magic: the Gathering maxim here: The only hit point that matters is the last one

7.1 How to open Challenge Rooms

Astute readers might have realized this by now, but the conditions for opening Regular Challenge Rooms and Boss Challenge Rooms are not mutually exclusive. Having exactly one or zero heart containers means you can fulfill both conditions at the same time and in doing so, increasing your chances for getting something good out of those rooms.

7.2 Outsmarting the Devil

It’s true that some items in the Devil Room cost you 1 heart, and some cost you 2. What the game never tells you is that there is a way to get more bang for your heart in these deals with the Devil.

Special Case 14: 2-heart deals with the Devil
It is possible to buy a 2-heart item in the Devil Room if you have only 1 heart container. It will only take away the one heart container

Sweet! This is why it’s important to bear in mind that the deals with the Devil have to be made in a specific order.17 With only 2 HP you can get both Ceremonial Robes and Brimstone, but only if you get them in that order.

But you have to be careful here as well. Deals with the Devil are also possible with zero heart containers, but in this case you get the short end of the deal.

Special Case 15: Deals with the Devil without heart containers
When you have zero heart containers, all Devil Room items cost you three Soul/Demon hearts.

This is awful. From a damage perspective, red hearts and Soul hearts are functionally the same, but if you don’t have any HP, all of these powerful items are 150-300% their original cost! Sometimes this cost is worth it, but it’s always preferable to pay less for exactly the same item.

There are also other ways of creatively using your health in Deals with the Devil

Special Case 16: Respawning as Dark Judas or «???»
The Devil Room items Judas’ Shadow and Ankh both give you an extra life. The trick is that they also respawn you with zero heart containers. For Judas’ Shadow you respawn with 2 black hearts and have the ability to gain further heart containers later in the run. With the Ankh you respawn with three Soul hearts and can no longer gain heart containers, gaining instead one Soul heart instead.
Special Case 17: Not today, Satan!
Some items in Devil Rooms give you Soul/Demon hearts immediately after pickup. These items are: The Mark, The Pact, Ceremonial Robes, Abaddon, Missing Page 2 and Empty Vessel

These items can be bought on your last heart container but since they give you extra hearts immediately, you won’t be killed for trading up your last heart.

Special Case 18: Dead Cat
Upon pickup, the item Dead Cat will set your heart containers to 1 and give you 9 extra lives, with the caveat that every time you respawn you only respawn with one heart container

The condition of setting your heart containers back to 1 might suck for some, but it’s also a way of cheating the Devil. Note that this item doesn’t reduce your heart containers, it just sets them to 1. This means that you can go into a Devil Room with only 1 heart container and buy 2 items with it. You just need to buy first the Dead Cat, then your HP is set back to 1 and you can buy the other item with exactly 1 heart! Even if this kills you, you still have 8 more lives ahead of you.

7.3 Life with one or less HP

We’ve seen how having exactly one heart container is useful for both Challenge Rooms and Devil Rooms, but there’s more about having one or zero heart containers.

Special Case 19: Dark Prince’s Crown
The item Dark Prince’s Crown gives you a passive bonus to range, fire rate and shot speed while you have exactly 1 red heart
Special Case 20: Whore of Babylon
The item Whore of Babylon grants you a passive bonus to damage and speed while you have 1/2 or less red hearts
Special case 21: Empty Vessel
The item Empty Vessel grants you flight and an occasional shield if you have zero heart containers

These three items are all about getting bonuses while on «low HP». There’s opinions on which of these is better, but I won’t pronounce them. I only present these as further examples of why having low Red Containers can be a good idea.

Special Case 22: Polaroid and The Negative
After unlocking them, Polaroid and The Negative drop after defeating Mom and taking one makes the other disappear. If Isaac gets hit while having 1/2 or less red hearts Polaroid will deploy a shield for a few seconds, and The Negative will deal damage to all enemies in the room

In order to get to the later levels (Chest/Dark Room) you need to take one of these. They both provide bonuses when hit at «low HP».

6: Health as a marker of ‘run health’Health in The Binding of Isaac8: Conclusions

  1. Namely: damage and fire rate. Speed and range as well, but on a secondary plane.↩︎

  2. I never thought I would type out that phrase in my life.↩︎

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