Some sentient items in D&D have spellcasting capabilities. For example, the description of the sentient magic greatsword Blackrazor says (DMG, p. 217):

Blackrazor can cast the haste spell on you once per day. It decides when to cast the spell and maintains concentration on it so that you don't have to.

However, Blackrazor does not have a Constitution score:

Blackrazor is a sentient chaotic neutral weapon with an Intelligence of 17, a Wisdom of 10, and a Charisma of 19. It has hearing and darkvision out to a range of 120 feet.

If a person is wielding Blackrazor and is under the effect of the haste spell cast by Blackrazor, can that spell's concentration be broken?

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    \$\begingroup\$ A reddit thread on /r/DnDNext about the same issue: Does Blackrazor make concentration checks when it is casting Haste? \$\endgroup\$
    – V2Blast
    Jul 27, 2022 at 17:07
  • \$\begingroup\$ @V2Blast From reading this one commenter refers to the Object Hitpoints section of the DMG (P.247) stating that Blackrazor technically has AC and HP as it is in object. Which would intimate a Con Save.....however again maybe the question should be, what is the Con score of a sentient weapon? \$\endgroup\$ Jul 27, 2022 at 17:27
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    \$\begingroup\$ @MatthewPerryman That's an interesting question too! But I hope that my answer clarifies why we don't actually need to know Blackrazor's constitution score in this particular context. \$\endgroup\$ Jul 27, 2022 at 18:39
  • \$\begingroup\$ I think it does. I will look at a few more sources then mark an answer soon. \$\endgroup\$ Jul 27, 2022 at 18:44

2 Answers 2


RAW (Rules As Written), Sentient Magic Items cannot lose concentration from Constitution Saving Throws

Sentient magic items are often formidable and powerful, and influence the world with wills of their own. However, for the purposes of the rules, there is some strong consensus that sentient Magical items are objects, and not creatures. There is also textual support for this interpretation: the DMG gives guidance for creating a sentient magic item, and states (DMG, p. 216, bold added):

Use the information on creating NPCs in chapter 4 to develop a sentient item's mannerisms, personality, traits, ideals, bonds, and flaws... ignore or adapt any result that doesn't make sense for an inanimate object.

This at least strongly implies that even though they are intelligent and capable of thought (and sometimes action) outside of their user, a sentient magical item is considered an object for the purposes of the rules. As such, they are subject to the rules for objects, including the following from the Player's Handbook (p. 185, bold added)

Objects always fail Strength and Dexterity saving throws, and they are immune to effects that require other saves.

They are subject to the rules on spellcasting in general, so they can lose concentration by dying or becoming incapacitated, having the spell's duration end, or by casting another concentration spell (PHB, p. 203-204). But the most common way of losing concentration for creatures is to fail a Constitution Saving Throw from either taking damage or environmental factors (ibid). And since sentient magical items are "immune to effects that require" Constitution saving throws, they will never lose concentration from (for example) taking damage, unless that damage destroys them or (if such a thing is possible) renders them unconscious.

It's also worth noting that many features of the game that impose the incapacitated status (e.g. the spell Tasha's Hideous Laughter, PHB p. 280) do so by targeting creatures, rather than objects. So sentient magical items are also difficult to incapacitate (or stun, or paralyze, etc.).

A DM could overrule any of these interpretations or rules, of course: they might declare that sentient magic items are creatures at their tables. But it's worth noting that the rules as written leave a lot of how that would work ambiguous (the best example is the one you mentioned: they don't have constitution scores, so how would they roll a Constitution save?). If you go by the rules as they are presented, it seems to me that there are very few things in the game that could cause a sentient magic item to lose concentration, other than killing it or making it concentrate on something else.

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    \$\begingroup\$ Out of curiosity, and this may be a separate question, but is an object incapacitated by default? \$\endgroup\$
    – SeriousBri
    Jul 27, 2022 at 19:20
  • \$\begingroup\$ Interesting question! Most objects the answer would be obvious (they can't take actions or reactions because there are none that they could take), but for a sentient item that can communicate that's a bit more unclear. As an example, could a sentient magical item that can perceive its surroundings use the Search action (PHB p. 193)? After all, it has a Wisdom score. Then again, it doesn't have a dexterity score, so what's its initiative? I think this might warrant its own question. But it's clear to me that Haste should not be ended by this "default" incapacitation. \$\endgroup\$ Jul 27, 2022 at 19:36
  • \$\begingroup\$ @SeriousBri After all, why even mention the spell if it always winks out of existence as soon as you cast it? Except... I suppose except that it means Blackrazor could give its user a round of inaction through the fatigue after the Haste spell ends this way... Huh. \$\endgroup\$ Jul 27, 2022 at 19:37
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    \$\begingroup\$ @SeriousBri even if they are, that's not a problem. Specific beats general so if generally they are, but specifically this one can concentrate, then it can concentrate. \$\endgroup\$
    – Mołot
    Jul 27, 2022 at 19:50
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    \$\begingroup\$ Anti Magic Field as the edge case, maybe mention that? It would remove the magic of anything that isn't an artifact, I think. \$\endgroup\$ Jul 27, 2022 at 20:00

I'll begin my answer with a caveat: I'm not sure this scenario will come up too often. With Blackrazor being the item casting the spell, per the rules on concentration, it would need to cast another spell (not applicable here), take damage, or be incapacitated or killed (not applicable either) in order to potentially lose concentration.

As a result, the sword would need to take damage to trigger a Constitution saving throw to maintain concentration. This gets into a larger question on whether a magical item can take damage (somewhat discussed in this answer). Irrespective of how magical items can take damage and how to track that damage, I think we should also keep in mind that it would be fairly unlikely that Blackrazor would take damage (though again, not impossible - for example, the rules on concentration describe a player being hit by a wave, which a DM could rule would in turn cause damage to the weapon and by extension trigger a Con save).

With that in mind...

RAW: unclear. As you've identified, Blackrazor does not have a constitution score, meaning we cannot know what would be rolled assuming a concentration check was necessary. All the description says is that the sword maintains concentration "so that you don't have to." As a result I think we have some interpreting to do.

Possible interpretations:

  • Concentration is automatically broken, since the sword does not have a Con score;
  • Assigning some Con score commensurate to the damage taken and the specific circumstances of the situation;
  • Automatically succeed, since the rules are silent on a Con score, and perhaps since Blackrazor is a legendary weapon (some good info on rarity of magic items in this thread).

At my table: I would probably "rule of cool" the situation. This is a legendary magic item, and it taking damage is such an edge case that I'd probably let the player keep Haste. But I think other DMs could reasonably disagree.

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    \$\begingroup\$ "for example, the DMG's description on concentration describes a player being hit by a wave, which a DM could rule would in turn cause damage to the weapon)." – This in the PHB/basic rules, not the DMG – but anyway, the concentration rules provide this as an example of "certain environmental phenomena" that the DM could decide forces a DC 10 Con save to maintain concentration. The rules don't say a wave would cause anyone to take damage. That said, the DM could still rule that those environmental phenomena affect sentient magic items in the same way they affect PCs, and call for a Con save. \$\endgroup\$
    – V2Blast
    Jul 27, 2022 at 17:03
  • \$\begingroup\$ You also say "(supported by the text on waves in the description of concentration, which encourages the DM to decide on a DC for the check)" – which is not the case. Once again, that rule specifies the DC: "The DM might also decide that certain environmental phenomena, such as a wave crashing over you while you're on a storm-tossed ship, require you to succeed on a DC 10 Constitution saving throw to maintain concentration on a spell." \$\endgroup\$
    – V2Blast
    Jul 27, 2022 at 17:05
  • \$\begingroup\$ I also agree with OP in the fact that this situation will not come up often. However the party have had some experience with the sword in the past and the players are clever enough to try and disrupt this ability so I am just trying to be prepared. \$\endgroup\$ Jul 27, 2022 at 17:35
  • \$\begingroup\$ @V2Blast thanks for the feedback, edited. \$\endgroup\$ Jul 27, 2022 at 18:20

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