Vulnerability and Why You’re Undervaluing It

Vulnerability is one of just a few true multipliers for damage. Not only does it give you twice your normal damage when fully stacked, but if combined with a good amount of vulnerability effectiveness, it can be more powerful than critical hits.

Since the season patch, some people have been lamenting the fact that they can’t seem to get enough damage out of their builds. Some of this is certainly due to buffs that enemies received, but some of it is also due to players struggling to find a replacement for the damage-per-debuff and/or explode-on-stun (both of these were in dire need of rebalancing).

I’d like to introduce you to vulnerability, or more accurately, re-introduce you, since the popularity of Diversive Tactics meant many people were already using it, just not for its primary purpose. But first, a digression into multiplicative vs. additive bonuses.

Multiplicative and Additive Bonuses

When two different stats apply to the same game behavior, they can be combined in different ways. While ultimately this could be any mathematical expression, it almost always breaks down to either multiplication or addition. Damage Reduction and Resistances are an example of multiplicative bonuses. If you have 60% damage reduction and 60% resistance to a source of incoming damage, you will take 1-(1-.6)*(1.-6) = 84% less overall damage than if you had none. If these two had been additive, then you would’ve taken 1-(.6+.6) = -20% damage (meaning zero). On the other hand, most damage bonuses are all additive. If you have a 15% ranged damage bonus from gear and a 50% damage bonus vs. debuffed enemies from the Cull the Weak perk, you will see 65% more overall damage when you are attacking debuffed enemies from range, not 72.5% more if it were multiplicative (1.15*1.5).

How does this help me increase my damage?

For values greater than 100% (i.e. things that cause numbers to increase), multiplicative bonuses are almost always stronger than additive ones. In some cases, they are a lot stronger. It’s easy to see why if we look at it visually. We’ll use the relationship between damage bonuses and critical hits as a running example. Let’s say you have three pieces of gear:

  • (Item A) +50% bonus damage
  • (Item B) +80% bonus damage
  • (Item C) +80% effective critical damage*

*For the moment, I’m going to completely gloss over how criticals actually work and just pretend that we have 100% critical hit chance and 80% equivalent critical damage (meaning that we’ll pretend all the complex crit stuff averages out to about 180% extra damage on a critical hit).

Bonuses of the same type are almost always additive, and bonus damage is no exception. If you have two, you add them. Criticals are a multiplier. When you crit, your bonus damage gets added together, then the entire thing is magnified (again, I’m hand-waving over the details, but “equivalent average critical damage” can be thought of this way).

Additive vs. Multiplicative Bonuses

Multiplicative bonuses can be very strong.

Vulnerability and Vulnerability Effectiveness

Vulnerability is a stacking multiplicative modifier. Every time you apply a stack of vulnerability, the enemy takes 10% more overall damage, and this can stack ten times, for a total of 100% more. For those of you counting at home, this doubles your damage.

It gets better, though. “Vulnerability effectiveness” is a lesser-known stat that enhances the effect of vulnerability. If you have the “20% effectiveness to Vulnerability debuffs” primary enchant, each vulnerability stack is now 20% stronger. So instead of 10% extra damage, it’s 12%; and instead of 100% extra damage at max stacks, it’s 120%.

This doesn’t sound like much, so let me introduce you to the Uncreator psalm. On the Neocore Compendium, the Uncreator’s effect is listed as “Vulnerability bonus increased from 10 to 15%”, but that’s not quite what it does:


That’s what it does. And it stacks.

For the cost of a single socket, this increases the vulnerability debuff by 50%. When two are equipped, the Uncreator rune adds with itself (so 50%+50% becomes 100%) and then multiplies the vulnerability debuff, giving 20% increased damage taken, for a total of 200% more damage taken at ten stacks. That means for just two sockets, vulnerability has gone from a 2x multiplier to all of your damage, to a 3x multiplier for all of your damage. Since “vulnerability effectiveness” multiplies “vulnerability”, and “vulnerability” multiplies damage, vulnerability effectiveness itself is a multiplicative stat (thanks, associativity). This means it scales very well into the end game and suffers diminishing returns only from itself, nothing else.

A typical character build will have anywhere from 10-15 open sockets (some will usually be reserved for various build-specific psalm-code doctrines). Let’s compare socketing straight damage bonuses (archeotech shards) with psalm-code doctrines and uncreator psalms:

  • Twelve Cognis shards (+15% ranged bonus damage), all of them on a weapon (obviously you can’t do this, but it’s a worthwhile thought exercise) is 180% bonus damage, not bad.

  • Three Phosphoenic/Binharic/Volkite/Terminus psalm-code doctrines (+100% heat damage each) would give 300% bonus damage (plus individual psalm effects), definitely better.

  • Now let’s fill them with twelve Uncreator psalms. Twelve psalms at 50% effectiveness each is 600%, which gives us 700% increased enemy damage taken with max stacks.

And remember, the first two will suffer diminishing returns with other sources of bonus from your gear and skills. So 300% additional bonus damage (normally a 4x overall boost) if you already have 400% bonus damage is only 2x more overall damage (300%+400% = 700% or 8x).

Vulnerability effectiveness is a straight damage multiplier, and Uncreator psalms provide gobs of it.

Building for Vulnerability

Of course, vulernability effectiveness only helps if you’re stacking vulnerability. If you want to incorporate it into your build, you’ll need a fast way to stack vulnerability, since dealing damage to an enemy without vulnerability stacks on them is not giving you any extra damage. Typically, this needs two things:

  1. Fast hits
  2. Chances to apply vulnerability

Channeled or persistent area of effect skills are far and away the easiest way to handle the first. Grav guns are the poster child here. Gravity Implosion (the fourth skill) is a sweet fire-and-forget AoE which rapidly and continuously hits enemies in its area. Gravity Surge (the third skill) is a channeled small-AoE effect which also rapidly hits enemies. Between these two, you can easily get half a dozen hits per second to a decent-sized pack of enemies. Other weapons and skills are definitely viable (flamers, shotguns, las-things of various sorts), and most of it is a matter of preference.

Chances to apply vulnerability are spread a bit thinner, but the best is usually vulnerability-on-crit. Almost all end-game builds have over 50% crit chance, and since vulnerability-on-crit is guaranteed on every crit, it’s a strong stat to collect. Furthermore, it stacks. So if you have two sources of vulnerability-on-crit, a crit will apply two stacks of vulnerability. The easiest source to get is the passive skill point in either the physical or heat passive trees (whichever you are using). If you want more, there’s an Archeotech Eye Implant and an Archeotech Signum that can both roll vulnerability-on-crit, and an Ancient weapon “Of Shattering” will also have it. You can use “chance to apply X vulnerability on X hit”, but the probabilities are a bit low compared to vulnerability-on-crit (although infinitely more valuable in maps that have crit disabled). It can’t hurt to have more, so if you have open space for it on gear, go for it.

It’s important to keep in mind that if you don’t stack vulnerability quickly, the ramp-up time can be a serious source of lost damage. If it takes just three hits to get 10 stacks, the first three hits are doing 0, 1/3, and 2/3 extra damage, respectively (assuming zero vulnerability effectiveness equipped). If an enemy dies in four hits, you’ve done 1+1.33+1.66+2 = 5 hits’ worth of damage, not quite the 2x you were looking for. If you’re putting up just one vulnerability stack per hit and your hits are coming every half-second, that’s 5 seconds of ramp-up and a lot of lost damage.

Parting Note

Neocore may end up deciding that Uncreator is a bit much. I wouldn’t blame them, though I think it would be best if other non-Uncreator sources of vulnerability effectiveness were increased in value and availability to make up some of the difference. If this happens, vulnerability itself does not really decrease in value. Sure, it wouldn’t be as easy to stack up, but it’s hard to discount the value of a 2 or 4x multiplier.