I'm wondering whether a character could spread holy water over his sword or axe and then hit an undead and on the first hit, inflict an extra 2d6 as if the holy water had been thrown at the undead. After all, we can do that with poison and holy water is like poison to undead creatures.


By the book? No.

As a house rule?

Consistency may be a problem. Poison for applying on blades is usually described as a paste or oil - something that can stick for a while, as opposed to an ingested poison which would be watery.

The holy water itself wouldn't stay on the blade long enough to hit something with. It may be able to (temporarily) make the weapon holy, but this would be entirely up to the DM, and not covered by the rulebooks.

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    \$\begingroup\$ What if I filled my scabbard with holy water? Then the first attack or two would presumably be more powerful. More importantly, why are we using swords instead of water pistols? \$\endgroup\$ – Jon Story Jan 12 '16 at 10:54
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    \$\begingroup\$ @JonStory "What if I filled my scabbard with holy water?" Presumably, your sword would rust. A blade that is not oiled corrodes very quickly. Holy water would slick right off an oiled blade. \$\endgroup\$ – LegendaryDude Nov 29 '16 at 16:57
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    \$\begingroup\$ In a very cold environment (glacial rift of the frost giants for 200, Alex) you could freeze it onto the blade. :) \$\endgroup\$ – KorvinStarmast Oct 5 '18 at 12:10
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    \$\begingroup\$ @LegendaryDude it's simple, we bless the oil. Holy oil. \$\endgroup\$ – Captain Man Oct 5 '18 at 12:55
  • \$\begingroup\$ If you fill the scabbard, the water wil lbe gone the moment you do any swing movement with the blade. Fill a dagger scabbard, take dagger out, hit enemy - MAY work, but swinging a sword? No. \$\endgroup\$ – TomTom Oct 7 '18 at 7:30

Shape water cantrip can coat the weapon for an hour

Work with your DM to use two of the features of the shape water cantrip to temporarily coat the blade (for an hour) with frozen holy water. This would work better in a very cold environment than in and around a pool of lava or a red dragon's lair.

By RAW, it should work.

From the Elemental Evil supplemental material1 (p. 21), you can apply two features of the spell and keep then going for an hour -- (1) shape the water to perfectly fit onto the weapon, and (2) freeze it into that shape.

Shape Water
Transmutation cantrip
Casting Time: 1 action
Range: 30 feet
Components: S
Duration: Instantaneous or 1 hour [depending on effect]

This effect can be used for at most one hour.

You choose an area of water that you can see within range and that fits within a 5-foot cube.

Holy water, in a vial, fits within a 5' cube. You could pour it into a bowl or helm while doing this to make the process easier, but that's something to work out with your DM.

You manipulate it in one of the following ways: [...]
- You cause the water to form into simple shapes and animate at your direction. This change lasts for 1 hour.
- You freeze the water, provided that there are no creatures in it. The water unfreezes in 1 hour.

If you cast this spell multiple times, you can have no more than two of its non-instantaneous effects active at a time, and you can dismiss such an effect as an action.

There's one weapon, coated with a nice layer of holy water for the next successful attack on a creature susceptible to holy water damage.

Do you really need to freeze it? Maybe not. Depending on how you and your DM interpret the spell effect, simply shaping it to the contours of the weapon might suffice. You could also shape it to fit as a weapon your are proficient with, if one of those is "a simple shape." Again, work with your DM to work out the fiddly details.

I would recommend that the damaging effect be limited to one successful hit against an undead creature, or fiend, that is susceptible to holy water damage such that the hit does the full vial's damage (2d6 radiant) when hit with the coated weapon. (Sort of like how poison doesn't last forever on a weapon). Otherwise, this approach would be a little OP in terms of using a cantrip to enchant a weapon.

1This spell is also in Xanathar's Guide to Everything (p. 164).

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    \$\begingroup\$ I like the idea, but would frozen holy ice still do damage or would it mostly just fall to the ground in pieces? \$\endgroup\$ – Hennes Oct 5 '18 at 13:21
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    \$\begingroup\$ @Hennes The idea is that it does damage on contact with the undead/fiend; that's the magical thing about the holy water. I can see your point. That's why the old "work with your DM" is a good idea here. (If you look at the spell description, you can dismiss any of the features .... so let it melt when you score that hit? Might be too fiddly at that point ... since it takes an action to dismiss ... ) \$\endgroup\$ – KorvinStarmast Oct 5 '18 at 13:33

RAW, you need to make a ranged attack with the holy water, as an improvised weapon.

It's right there on PHB151

Should you houserule it, I would suggest that allowing the full effect of the holy water in addition to the effect of the underlying weapon breaks the action economy. Also, possibly the holy water economy.

  • \$\begingroup\$ Yes. I know you can throw it. I was wondering about the application on a weapon as that does not seem to be mentioned and thus probably no allowed. \$\endgroup\$ – Alexis Wilke Jan 12 '16 at 1:42
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    \$\begingroup\$ About the economy, some spells allow you to add some damage similar to that to your weapons and such last for the duration of the spell, so I do not think it would be that bad. \$\endgroup\$ – Alexis Wilke Jan 12 '16 at 1:43
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    \$\begingroup\$ Oh, here's an idea - make a melee attack with the holy water as an improvised weapon! Basically, smash the flask over them. Not entirely RAW, but close. \$\endgroup\$ – Adeptus Jan 12 '16 at 1:55
  • \$\begingroup\$ @Adeptus which is probably a much-better way to implement the close-in holy water attack than applying the disadvantaged 5' ranged attack that RAW provide for.... \$\endgroup\$ – nitsua60 Jan 12 '16 at 2:10
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    \$\begingroup\$ A non-improvised weapon for delivering holy water is the aspergillum: en.wikipedia.org/wiki/Aspergillum \$\endgroup\$ – Sebkha Jan 14 '16 at 12:50

I brought this same idea up to my DM because I wanted to apply Holy Water to my arrows or rapier (I'm playing a rogue that likes to use poison: holy poison!).
The house rule we came up with was I have to make a 20+ poison check to craft a poison from the holy water with my poison kit.
A successfully crafted poison using this approach deals 1d6 radiant damage to a fiend or undead. That's a combination of (1) rules on how to apply poison to weapons, (2) the rules on holy water doing radiant damage, and (3) using an ability check per Chapter 7.

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    \$\begingroup\$ Could you expand on this by showing that this isn't an option by default (probably by summarizing where you and your GM looked for information before making the homerule) and expand on how this rule has performed in-game? \$\endgroup\$ – Ifusaso Aug 26 '20 at 13:44
  • \$\begingroup\$ I like the idea of being able to use an oily element so it sticks to the weapon, like we do with a poison. As for an arrow, I'm wondering how much of it would really stick to the tip... maybe the damage could increase by just 1d4. \$\endgroup\$ – Alexis Wilke Aug 26 '20 at 19:37

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