Would a magic item that lets you cast a spell (that normally requires concentration) without needing to concentrate on it be unbalanced?

Question

I am designing some magic items and would like to add some abilities like the following to some of the items:

While holding this item you may cast one of the following spells from it, using your spell save DC and spellcasting ability modifier: x, y, z. When you cast a spell this way, you cannot do so again until the next dawn.

This is pretty standard, usually it works with charges but when it's one spell per day I don't need them.

Now I was wondering about spells that require concentration. Let's say I wanted to add something like Enlarge/Reduce, Bane, Bless, or Bestow Curse. Normally, this would still require concentration but I would like to get rid of that because:

• It would be sad if the user gets hit unkuckily next turn and the item's daily power is wasted.
• I would like the characters to be able to use their own concentration spells unhindered while using the daily power.

Generally, concentration serves two purposes which would potentially be undermined this way:

1. Prevent stacking multiple powerful ongoing effects. I think this is unproblematic because the item can be used only once per day. Theoretically, a player could get multiple such items but I think this is handled by attunement and the usual vigilance requires when giving out magic items.
2. Offer a possibility to opponents to make the effect end early. I think the necessity of this depends strongly on the spell being used. I don't think the spells I listed above would make this necessary.

I assume there will rarely be a need to end such an effect early but if necessary I would include the option to end any such effect as a bonus action.

Is my analysis reasonable? Are there other problems I failed to account for?

Answer 1

This is entirely reasonable, and even comes with a precedent. Potions (and a few other magic items)

First off, we have this from the DMG:

Many items, such as potions, bypass the casting of a spell and confer the spell’s effects with their usual duration.

Then to look at a few examples

Potion of Diminution

When you drink this potion, you gain the "reduce" effect of the enlarge/reduce spell for 1d4 hours (no concentration required).

Potion of Gaseous Form (Which gives you your precedent of shutting the spell off as a bonus action)

When you drink this potion, you gain the effect of the gaseous form spell for 1 hour (no concentration required) or until you end the effect as a bonus action.

Potion of Heroism

For 1 hour after drinking it, you gain 10 temporary hit points that last for 1 hour. For the same duration, you are under the effect of the bless spell (no concentration required).

And so on. Potions that give you spell benefits bestow the effect of the spell without actually casting it (which also bypasses things like Counterspell) and do not require Concentration.

In the case of Enlarge/Reduce or Bless you're effectively giving them 1 potion per day--but it can be counterspelled.

The key place this gets different is that you're including offensive concentration spells--which don't match with potions, but there are other magic items that do this.

The Shield of the Uven Rune gives us use of the Bane spell

Bane. You can cast the bane spell from the shield (save DC 17). The spell does not require concentration and lasts for 1 minute. Once you cast the spell from the shield, you can’t do so again until you finish a short or long rest.

Far Gear (and a few other items) gives us creature summoning

Aberrant Ally. You can conjure an aberrant creature from the chaos of the multiverse to serve you. This functions as the conjure celestial spell (no concentration required), except the creature you summon is an aberration of challenge rating 4 or lower. Once you use this feature of the far gear, it cannot be used again until the next dawn.

And, lastly, the Shield of the Hidden Lord gives us a purely offensive concentration spell

The shield has 3 charges. You can use an action to expend 1 charge to cast fireball or 2 charges to cast wall of fire from the shield (save DC 21 for each). The wall of fire spell lasts for 1 minute (no concentration required). The shield regains all expended charges daily at dawn.