Are the following anti-magical items balanced?

Question

All the following items are part of one big ritual that disrupts magic for an entire world. I want each of the items by themselves to be a item of less power, but fitting to the theme of anti-magical, like disrupt or block magic etc. Are there any grave balance problems with the following items? I tried to stick to existing spells where possible, because I am not very experienced in home-brew.

• Item 1 (Very rare): While wearing this item you can 1/day cast the spell Antimagic Field without expending material components or a spell slot.
• Item 2 (Rare): This item has 4 charges. You expend one of these charges to cast the spell counterspell at level 3 without using a spell slot. You can expend extra charges to cast the spell at a level equal to 3 + amount of additional charges spent. The item regains 1d4 charges each day at midnight.
• Item 3 (Shield, Uncommon): When holding this shield, if you are subjected to a magical effect that allows you to make a Dexterity saving throw to take only half damage, you can use your reaction to take no damage if you succeed on the saving throw, interposing your shield between yourself and the source of the effect. (taken from Shield master feat)
• Item 4 (Cloak, uncommon): 1/day you can ward yourself against magical attacks for 8 hours. Until the spell ends, any creature who targets you with a harmful spell must first make a Wisdom saving throw. On a failed save, the creature must choose a new target or lose the spell. This spell doesn't protect you from area effects, such as the explosion of a fireball. If you make an attack, cast a spell that affects an enemy, or deal damage to another creature, the protection ends. (adapted sanctuary)
• Item 5 (rare): 1/day you can disrupts the concentration of anyone in a 20 foot sphere centered on a point up to 30 feet away. The affected creatures loose concentration without a saving throw. (this is a dangerous one, there is no such spell)
• Item 6 Brooch of Shielding(uncommon, requires attunement)
• Item 7 (Armor, rare, requires attunement): resistance against magical weapon attacks (based on armor of resistance)
• Item 8 (Bracelet, legendary, requires attunement): While wearing this item you have resistance against magical damage from weapons and spells.

Why do I want these items? For my campaign my BBEG wants to remove all magic from the world. Sort of like a permanent anti-magic field that is world wide. To accomplish that he needs to make a ritual with some magic items. I don't want the items by themselves to be useless, so I want them to be magic items on their own. They combined can erase magic from an entire worlds, so each of them should have some power that is sort of anti-magic. Either stop magic or protect from it or similar. That is how I came up with the 8 items you see on top. If you know any existing items other than the brooch of shielding that fit this theme, I would happily take them over home-brewed items as they are probably better balanced. But I haven't found any others.

Also the magical rareness of the items is only semi-important, because the party is gonna get all of them sooner or later either while stopping the BBEG or if they are faster. The rareness only helps me decide in what order they get them.

Lastely, I hope this is a valid question for this stackexchange. I have seen other people asking about the balance of their home-brew, so I think it should be fine. If it is not, please explain to me why or how I can change the question to be accepted.

Answer 1

Note: I'm not experienced at balancing homebrew content. I am simply comparing these items to official (DMG) material assuming it is balanced.

Item 1 is overpowered

Anti-magic field is an 8th level spell. an 8th level one-time use scroll according to DMG page 200 is a very rare item. So one that refreshes every day should be at least legendary, but even that might be too powerful.

Item 2 is inconclusive

there are several wands, such as wand of fireball that have up to 7 charges of 3rd level spells and recharge 1d7 of them at dawn, so that would suggest that 3rd level counterspell that has only 4 charges and recharges 1d4 of them would be underpowered. But that does not take into account action economy - to use wand of fireball you have to use an action, but counterspell can use reaction. Given the fact that most of the time most characters don't get an option to use reaction that makes this item much more powerful. I haven't found a good analogue for this in official materials, so the value of 3rd level spell charges vs 'free' reactions is debatable.

Item 3 is at least rare

The closest analog to this is Mantle of spell resistance which is rare and states:

You have advantage on saving throws against spells while you wear this cloak.

First we have to evaluate the difference in benefit on all spell saving throws vs Dexterity saving throws. If we assume that spells are equally likely to use Dexterity, Wisdom, Constitution or one of the other stat saving throws that means this artifact is about 1/4rd as good as Mantle of spell resistance.

Second we have to evaluate the relative power of the effects. If the saving throw is likely to succeed 50% of the time, this item will reduce damage by average of 75% (50% on fail and 100% on success) while the Mantle of spell protection will only reduce damage by average of 12.5% (25% of time(if first roll fails but second succeeds) by 50%). That makes the effect of this item 6 times stronger than Mantle of spell protection.

As a result this seems to be about 50% stronger, but less versatile item than Mantle of spell resistance, so it should be at least as rare if not more so.

Item 4 likely underpowered

Currently it does not specify DC of the saving throw, that makes it impossible to tell how often this ability will come into effect, but generally if you are fighting in a party or with minions and the caster has more than one enemy in range, the usefulness of this ability would be quite limited, because choosing the second best target for a spell is usually almost as good as choosing the best target. There might be some enemies that have only limited ranged spells, but even then the fact that the effect and on any aggressive action mean that the item is useful in only very niche circumstances.

Item 5 is probably ok

As you said there are no equivalents of this item anywhere in the official rules as there are no items that guarantee breaking concentration, especially not for a group of creatures. But there is a spell Magic Missiles which makes the target roll 3 concentration checks without any chance to avoid them, and you can get it from uncommon item Wand of Magic Missiles with 7 charges 1d7 of them recharging each day. Changing 3 concentration rolls to guaranteed failure, removing damage, but giving area of effect (which might not be that useful unless casters are plentiful) while increasing rarity seems quite fair.

Brooch of shielding is balanced

My method of evaluation is comparing items to official content. As Brooch of shielding is official all I can say is that it is balanced

Item 7 gets better with tougher foes

Evaluating this item is tough because while it seems very similar to armor of resistance and magic weapons seem to be about as frequent as some of the damage types the problem is that magic weapons are mostly possessed by higher level opponents unlike damage types which are distributed more randomly or based on theme. That means that this kind of armor would be next to useless for one facing low level mundane enemies such as brigands and orcs, while being extremely useful in battles against fiends and high level adventurers (unless they have backup non-magical weapons).

Item 8 seems close to balanced

Looking at Legendary items that provide protection against spells there are Ring of spell turning, Robe of Archmagi and Scarab of protection - all of which give advantage to saving throws, but also have additional effects. While resistance is clearly superior when targeted by spells that are used primarily for dealing damage, most of them can also be partially mitigated by succeeding on saving throw while resistance does nothing against crippling debuff spells. In the end resistance vs advantage on saving throws seems quite close, so this item seems quite balanced.

Answer 2

I can imagine some campaigns in which these items would be very, very unbalanced. For example, many campaigns feature prominent villains who deal damage through spellcasting; if a martial character gets your item #1 and casts antimagic field, that martial character can pretty much kill that villain and there's not even much point in playing out the battle.

(Normally antimagic field is balanced because you don't get to cast the spell unless you're a primary spellcaster yourself. A wizard isn't going to cast antimagic field and then walk up to the villain and stab him to death; a barbarian will totally do that, given the opportunity. A wizard who wants to antimagic somebody has to cast this spell and then keep his mostly-defenseless self within ten feet of the villain; a barbarian doesn't care.)

But there might be other campaigns in which these items would be pretty much irrelevant. For example if your adventurers are being attacked by orc barbarians, none of those guys have any magic anyway so most of these items are worthless.

(Some of the items are still useful if your group is worried about friendly fire. For example maybe one character wades into the melee and everyone else throws fireballs, but the character who's getting hit by the fireballs is taking less damage from magical effects.)

What sort of abilities does your BBEG have? How hard are these items going to shut him and his minions down?

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The great thing about being the DM is that you don't have to worry about balance relative to other campaigns -- you just have to worry about balance relative to the villains your group will fight in your campaign. If you want to hand out these items, that's totally okay. You'll just have to think carefully before letting the group battle a villain that uses a bunch of spellcasting.

(Honestly I think the antimagic field effect is too good. The rest of these effects are stuff that spellcasters could overcome, if they used enough damage, or if they used non-damaging save-or-lose attacks. The antimagic field effect is on a different level entirely.)