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My GM gave me a spear, which appears to be a homebrew item. It does 2d4 acid damage for 1d4 rounds in addition to the normal 1d8 base damage. If I attack a foe with this weapon each round how does the acid damage stack when applying new acid damage each round?

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  • \$\begingroup\$ I believe my GM created the weapon in Homebrew. I looted it. \$\endgroup\$
    – Lutorius
    Nov 11, 2018 at 6:50
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    \$\begingroup\$ Very, very closely related: Do duration damage spells stack with themselves? \$\endgroup\$
    – BBeast
    Nov 11, 2018 at 7:48
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    \$\begingroup\$ The site can evaluate homebrew material, but not without more information. Did the GM give you a formal entry for this magic item—as if it were from an official Pathfinder book—, including its description, prerequisites, and price? If not, ask for that. (You'll need to know caster level in case it's the target of a dispel magic at least, and you really wanna know if it's worth a fortune so you should sell it instead of keeping it!) Once you get it, add that information to the question, and the question should get reopened pretty quickly. \$\endgroup\$ Nov 11, 2018 at 10:49
  • \$\begingroup\$ That weapon just screams "bookkeeping nightmare" to me....Ok creature A still has 2 rounds left (roll dice), creature B has 1 round left (roll dice)....ask if he can just make it a flat extra 1d8 on hit :) \$\endgroup\$ Nov 12, 2018 at 20:31
  • \$\begingroup\$ My GM didn't have a lot of information for me when I asked. I looted it off of some custom mobs he created for a section of the adventure in the Rise of the Runelord campaign. There were three undead paladin like enemies involved in the fight with Lucrecia. One of the enemies was carrying this weapon. He didn't have it listed as masterwork or higher. \$\endgroup\$
    – Lutorius
    Nov 14, 2018 at 1:24

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As this is a homebrew item, the true answer is 'whatever your GM decides'. But it is reasonable to consider whether there is any precedent for such an ability to guide such a decision.

In brief, your spear seems to replicates acid arrow's effect, although there is disagreement on whether that stacks. Many damage-over-time effects don't stack, but this isn't necessarily a hard rule. The stacking damage version of your spear is considerably stronger than the non-stacking version. The non-stacking version will likely lose relevance at higher levels. Your GM should consider how powerful a weapon they are willing to give you.

For my full reasoning, read on.


Your spear appears to replicate the effect of acid arrow, but in melee rather than at range and with a randomised duration. Thus, we can ask whether the effects of multiple acid arrows stack. Since magic items and spells are both magical effects, answers about equivalent spells should be applicable to magic items.

However, the answer to whether acid arrow stacks is not particularly clear. There is some disagreement over whether the effects should stack (the two answers of the linked question argue opposite stances).

The rules on combining magical effects are phrased in a manner which addresses bonuses and penalties rather than sources of damage over time, which leaves some wriggle-room. The most relevant statement reads:

In cases when two or more identical spells are operating in the same area or on the same target, but at different strengths, only the one with the highest strength applies.

One could argue that this would imply that the effect does not stack. But in the case of acid arrow, it is still ambiguous, because the effect of the spell is creating some acid then throwing it at the target, not directly inflicting damage-over-time to the target (although this is also debatable). Whether these arguments hold for your acid-spraying spear is another matter.

Now, if you and your GM can decide whether acid arrow's effect stacks with itself, then it would be reasonable to apply this to your spear. If you can't develop a satisfactory answer, though, then we can turn to other damage-over-time effects.

One such damage-over-time effect is catching on fire. There is nothing to suggest that being on fire can have multiple instances which stack. A character is either on fire or they are not. The same holds true for bleed, which is explicitly not cumulative. Perhaps your spear works similarly: they are either drenched in acid or they are not, in which case hitting a target multiple times will just reset the duration.

However, catching on fire and bleed are generic conditions, and the rules for your magic item are more specific, so the rules for bleed and catching on fire might not apply.

A possible counter-example is alchemist's fire, which inflicts an extra 1d6 damage the round after the initial hit. It is not magical, for there is nothing suggesting otherwise, so the rules for stacking magical effects don't apply. The effect it inflicts is not the same as catching on fire, although it is deceptively similar. And there is nothing to suggest that its effect does not stack if you were to hit a target with multiple alchemist's fire in one turn. It's effect is to deal damage on the turn it hits, then again on the following round, and it is common for someone to deal multiple instances of damage to one target.

Looking at these, damage-over-time effects in Pathfinder lean towards not stacking, although this is not a clear-cut all-encompassing rule.

If your GM is still undecided after considering these factors on how to rule on the working of this weapon, another thing to consider is balance.

If the damage over time stacks, your spear will deal, on average, 12.5 acid damage per hit (15 if you also get 2d4 acid damage when you hit without counting towards the rounds of damage). In practise, the amount will be slightly lower, since enemies will often survive less than 1d4 rounds. A corrosive weapon deals an average of 3.5 acid damage per hit. 2d4 damage is already more damage than the 1d6 granted by a typical elemental weapon, and your acid spear inflicts that damage multiple times. The total damage output is comparable to a weapon with two or three elemental enchantments (flaming, frost, shock, corrosive), depending on how much weaker you consider damage over time compared to immediate damage, putting it on par with a +3 or +4 weapon. If this weapon is intended to have the value of a +3 or +4 weapon, then this is appropriate.

If, however, the instances of acid damage don't stack, then the acid damage per round will stay constant regardless of how many hits you get, at an average of 5 acid damage per round. If you only have one attack per round, this is still stronger than a regular +1 corrosive weapon (N.B. all magical weapons have, at minimum, a regular +1 enhancement bonus on top of their other effects. Corrosive costs an extra +1, so the +1 corrosive weapon has the value of a +2 weapon), so you might regard your spear as being worth a +3 weapon. However, if you have multiple attacks per round, then this value quickly drops off unless the spear does extra damage on a hit beyond the damage-over-time, as the acid effect is a flat 2d4 (average 5) per round regardless of how many hits per round you deal. The power of the spear in the non-stacking case is thus somewhere between a +2 and a +3 weapon, and would quickly become irrelevant compared to other magic weapons once you can reliably deal two or more hits per round.

If your spear deals bonus damage on a hit, separately to its damage-over-time feature, increase its relative value by about +1.

One final consideration: the case where the effects don't stack is easier to track because you only have to know how many rounds are left on the effect. If separate instances of acid did stack, then you would have to track the duration of each of those instances separately, and that could get tedious.

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  • \$\begingroup\$ Would it be fair to say that additional hits with this weapon only replaces the 2d4 damage if the roll is higher and otherwise just adds to or refreshes the 1d4 timer in some way? \$\endgroup\$
    – Lutorius
    Nov 14, 2018 at 1:26
  • \$\begingroup\$ That sounds reasonable. You could re-roll damage each turn rather than when the effect is first applied to avoid having to balance duration against damage. \$\endgroup\$
    – BBeast
    Nov 14, 2018 at 2:42

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