During the planning process of a new character I came across the following question.

What is the damage when you get a critical hit with acid arrow?

Lets take a look at acid arrow cast at CL3, and lets assume we confirm the critical hit. This means we have the initial damage, plus one round.

I haven't found anywhere which disagrees with the damage from the initial hit benefiting from the critical multiplier. Its an attack spell that requires an attack roll after all, and is not precision damage.

What seems to be in question is the damage of the following round. Is it 2d4 or 4d4 each following round?

If we look at other spells that require an attack roll, lets take shocking grasp cast at CL3. On a regular hit it deals 3d6, but when you crit it deals 6d6. At its highest it would be 5d6 to 10d6.

So why would a lower level spell be allowed to out damage a higher level spell? Yes the higher level spell can eventually deal more damage, but that can also be negated, and takes longer to build up.

The critical hit rules are fairly silent about this as they simply state spells can crit and that damage is doubled. Thats fine for instantaneous spells like shocking grasp, but it leaves out duration spells.

A spell that requires an attack roll can score a critical hit. A spell attack that requires no attack roll cannot score a critical hit. If a spell causes ability damage or drain (see Special Abilities), the damage or drain is doubled on a critical hit.

This question is much the same but is for D&D 5e.

There was a forum about this topic but it doesn't answer the question well.

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    \$\begingroup\$ It may be worth noting that (probably because [Acid] is valued greater than [Fire], [Cold], and [Electricity], more closely to [Force]) acid arrow is almost always weaker than shocking grasp, whether they crit or not. Acid arrow averages 3.3 or less damage per CL (down to 1.6 at CL 18) while shocking grasp is a static 3.5 though CL 5, but falls off harder (they cross around CL 12, but with AA still taking 4+rounds to "catch up"). \$\endgroup\$
    – Ifusaso
    Jan 27, 2020 at 19:49
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    \$\begingroup\$ That's not to say it can't be useful (I made an Acid sorcerer that harassed many a spellcaster with the sustained damage rules for Concentration at low levels), only that comparing it to other damage spells might not be the best way to gauge if its crit damage is "fair". It doesn't follow the existing spell design rules \$\endgroup\$
    – Ifusaso
    Jan 27, 2020 at 19:52
  • \$\begingroup\$ @Ifusaso I agree that fire/cold resistance is extremely common. I would have expected acid to be next, then electricity. Force is like the ultimate as there is little to nothing that decreases it. \$\endgroup\$
    – Fering
    Jan 27, 2020 at 20:11
  • \$\begingroup\$ I think the justification is touch/no Save/no SR. It's is still measly damage at most levels of play unless you invest pretty heavily in it. Some other sources of [Acid], notably Corrosive Touch, have similar reduction though. Still trying to find if there's a clear cut answer to this (I know what I think and how I'd rule it, but that may or may not be rules-accurate as far as I can tell) \$\endgroup\$
    – Ifusaso
    Jan 27, 2020 at 20:51

1 Answer 1


The ongoing damage cannot be a crit.

When you cast Acid Arrow, it requires an attack roll. Since you're making an attack roll, it can be a crit. The subsequent damage does not require (or even allow) attack rolls, and without an attack roll, it can't be a crit. Effects that create ongoing damage do not multiply on a critical hit unless they are specifically called out to do so.

Acid Arrow

An arrow of acid springs from your hand and speeds to its target. You must succeed on a ranged touch attack to hit your target. The arrow deals 2d4 points of acid damage with no splash damage. For every three caster levels you possess, the acid, unless neutralized, lasts for another round (to a maximum of 6 additional rounds at 18th level), dealing another 2d4 points of damage in each round.

The key is that this is not a continuation of the initial damage, but it is instead additional damage.

  • 1
    \$\begingroup\$ I cant accept this as an answer unless you can provide an actual rules quote or even designer comment. The on going damage is still part of the damage of the attack roll. Are you able to provide an example of ongoing damage that specifically calls out that a crit doubles the ongoing damage? \$\endgroup\$
    – Fering
    Jan 27, 2020 at 23:00
  • \$\begingroup\$ They main key to this is how the spell is worded. They don't "take the damage again" rather, the spell specifically states that the target takes "another 2d4 points of damage". It's not multiplied because it isn't a continuation of the initial damage, it's additional damage dice, and additional dice aren't multiplied on a crit. \$\endgroup\$ Jan 28, 2020 at 13:35
  • \$\begingroup\$ Ah, but I was using acid arrow as an example when the question was about duration spells in general. Yes acid arrow is worded that way, but I would still argue that all damage of the spell gets doubled unless otherwise stated. \$\endgroup\$
    – Fering
    Jan 28, 2020 at 14:08
  • \$\begingroup\$ The majority of damage spells are instantaneous, and don't do damage over a duration. The ones that do are either are save-or-sucks or AOEs (like wall of fire) that don't require an attack roll. Acid arrow is fairly unique in that respect. \$\endgroup\$ Jan 28, 2020 at 14:26
  • \$\begingroup\$ I cant check into this at the moment, but I know you are right in that there are more instantaneous damage spells compared to duration (at least at low levels). \$\endgroup\$
    – Fering
    Jan 28, 2020 at 14:43

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