[2021] Petrified Blood: A Mathematical Analysis

The gem info was released and the general consensus seems to be that the new Petrified Blood skill looks like a disappointment which simply isn't worth the cost. It's certainly true that it's more disappointing than people were expecting it to be (since we expected it to scale in a more meaningful way at gem lvl20), but it's still not that bad. Let me explain.

Here's the quick/simple summary of what the skill does:

1. You reserve 35% of your mana.
2. Once you're at low-life (below 50% life), you gain a defensive layer.
3. This defensive layer staggers hits against you, turning 40% of the hit damage you take into a DoT applied over 4 seconds.
4. Your life recovery can no longer heal you above low-life (Leech & Regen), with potions being the exception.

What we learnt from the gem info at lvl20/20 is that out of the 40% hit damage converted into a DoT, you only take back 30% damage as the DoT (At a rate of 7.5% of the hit/sec). This means 10% of the hit damage you took essentially disappears.

So you gain 10% pure damage reduction, and 30% of damage is converted into a DoT over 4 seconds... This seems like a no-brainer buff right? It's not.

There are a lot of costs associated with using this skill, and we'll go over each of them in detail.

Being Low-Life

The petrified blood "buff" is only active while you're below half health. Assuming you have ludicrously high life recovery which is such insane overkill that the 7.5% hit dmg/sec is negligible to you.... You're gaining 40% damage reduction... At the cost of 50% of your life pool... This is a net negative of 10% eHP (Effective HP) against hits.

If we're being realistic, your life recovery won't be that high without heavy investment (which could be spent on other defenses or dmg), so you're probably going to be losing 20%+ eHP.

While the staggering effect is a cool defensive layer on paper, it's still a net negative in your tankiness.

Oh, and other DoTs against you have double effectiveness now, because the stagger buff does nothing against normal DoTs... So you've halved your health for no defensive benefit.

Not being Low-life

Some people have theory crafted the idea of not being at "permanent low-life", by not reserving their life, and just using Petrified Blood as a situational defensive layer that helps them out in dangerous situations. Essentially, this way you still have access to your full health pool, so you aren't giving up the 20%+ eHP.

So what's the upside here? It averages out to 5% pure damage reduction, and 15% of hit damage being staggered into 3.75% dmg/sec... Honestly not too bad.

The downside is your leech and regen averages out to being cut in half, AND leaves you more vulnerable to one shots due to your recovery mechanics capping out at half health.

Sure health potions can take you back up to full, but even then, you're giving up 50% of your recovery for 5% dmg reduction and a 15% stagger... That alone is kinda questionable, but then add to that the need for constant life flasks, and you're more open to one shots, and you need to reserve 35% of your mana? Nah chief, this aint it.

The Reservation Problem

Lets say you're totally fine giving up 20% of your eHP for the buff, because you need to be at low-life for whatever reason... The defensive layer is worth it to you, or you want to use Pain Attunement or other unique gear that benefits from this... You still need to give up 35% of your mana for the reservation, which could be spent on better auras, whether they be offensive or defensive, which come with no downside.

So not only are you cutting your eHP (or your Recovery), but on top of that you're losing out on the opportunity cost of reserving something better.

But wait, you aren't technically giving up 35% of your mana, because it's opening up the possibility to use 50% of your life for aura reservations instead right? So you're actually "gaining" 15% reservation resource? Well... Sorta...

The new Arrogance support gem (Updated Blood Magic gem for Auras) has a mana multiplier of 201%, meaning you can only use a 25% aura with your life reserves.

The net result is that you're giving up a 35% aura slot for a 25% aura slot. This is a 10% net loss.

Honorable Mention: The Prism Guardian unique shield is pretty dope in this situation, since it actually frees up a TON of reservation resource, and actually makes the 35% mana reservation more than worth while... But then you're giving up your off-hand slot to use this shield, so more opportunity cost.

Pros & Cons

So here's the breakdown of the cons:

1. You have a net loss of either 20%+ to your eHP, or 50% of your life recovery.
2. You have a net loss of 10% of your reservation resources (unless using Prism Guardian)
3. You have a net loss of 100% to your eHP against incoming DoTs (if low-life build).

The benefits?

1. The use on Pain Attunement (30% more spell damage)
2. The use of the new Bloodthirst support gem (massive flat attack damage)
3. Any other low-life uniques, such as Loris Lantern etc
4. Recovery mechanics that scale on percentages of max health are technically doubled in effectiveness (if low-life build).
5. Overleech.

In regards to point #4, while it may sound tempting to double the effective recovery (eg 10% life regeneration becomes 20% life regeneration, and same for leech cap), It isn't as good as it sounds, because most of it will be spent on mitigating the stagger damage... However, if you're playing an ascendancy that gets to sky-rocket these numbers really high, yeah, it becomes way more beneficial and worthwhile.

As for point #5, Yeah, overleech. Like Slayers overleech. This is one of the properties of Petrified Blood that not too many people seem to be discussing or considering, and it's a huge one in my opinion.

Assuming you reserve only 49% of your health, and since Petrified Blood stops your life recovery at 50%, it means the last 1% of your health will never recovery... So you never reach full life... Which means Leech instances don't go away. You literally get one of the best Ascendancy nodes in the game.

Conclusions

The skill should pretty much only be used if you're planning on committing to a low-life build in my opinion, since the most meaningful benefits, the damage from PA/BT, and the Overleech, only effect you while on low-life.

So while on low-life the question becomes, is:

Loosing 20% of your life + Receiving double Degen damage + 10% mana reservation.

Worth being able to use:

30% more spell damage or massive flat attack damage + Overleech with double recovery.

For builds that gain eHP from other sources, such as Corrupted Soul ES, or MoM Mana, with tons of regen... Yeah this is a feasible skill that gives you good damage at a slight loss of defense.

For builds that rely purely on life for eHP, this makes you a glass-canon. You'll be extremely vulnerable to one shots and degens (the two things that kill you most in this game), and it just doesn't provide enough damage to compensate for that loss in my opinion... If you're pushing for those big dick numbers on Softcore and don't care about the deaths, go for it i guess... But honestly if you don't care about your defenses, you have no need for Petrified Blood in the first place, and are better off spending that 35% mana on more damage auras... So yeah, don't bother.

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