So... My players broke a piece off a magical trap

[Lupine]

As the title says, I had a trap that was storing magical energy, and then zapping the party with it. I'm now left curious as to what a large blue, eminently magical crystal might be, as a magical item. The party is 8 (yes, I am running for 8 players)

Right now, I'm thinking maybe a Gem of Brightness, but I just wanted to pulse the playground, and see what you all think could be fun items to give them (either DMG or Homebrew).

Cheers!

[False God]

It does what it says on the tin, if they can make it work. You put magic energy into (by casting a spell on it) and the next round it zaps the nearest target for some amount of damage (maybe 1d6/spell level?).

Otherwise it just glows dimly and is pretty.

[Zhorn]

The gem is mostly an arcane capacitor.
When it is exposed to magic it absorbs an amount over time.
When it reaches capacity, the next/closest creatures within range X are treated as conduit points to discharge said energy as Force Damage.
After discharge the gem is depleted and starts to absorb nearby magic over time again.

In most normal areas it is charging slow enough as to not be all that big of a risk to those handling it.
Being on a person that is either casting, targeted by, or in the area of a spell supplies a charge to the gem equal to the level of the spell.
When the charge reaches level Y, the gem glows, warning of a sufficiently harmful amount of energy being stored.
When the charge reaches level Z, it discharges instantly on the next valid creature to be within range of the gem (include the holder).

While it is glowing, but not at discharge levels, it can be used as a Pearl of Power, safely depleting the gem of the current charge.

A skilled arcanist had previously set up the trap this was part of to include sigils and arcane inscriptions on the room/device it was installed into to passively charge it from the latent magic of the weave, allowing the trap to be reset fast enough to serve as a defense. Such designs require too much space to function effectively on a small/portable scale.

[Unoriginal]

It does what it says on the tin, if they can make it work. You put magic energy into (by casting a spell on it) and the next round it zaps the nearest target for some amount of damage (maybe 1d6/spell level?).

Otherwise it just glows dimly and is pretty.

A sidequest where they meet an Artificier who offers to turn that stone into a magic gun could be pretty fun.

[J-H]

What did the trap do?

Maybe it will function as a spell storing item storing a small number (3?) of charges maximum, and only of a certain level and type. If it was a Lightning Bolt trap, then it'll store up to 3 charges of electric-damage spells no higher than 3rd level.

[Cicciograna]

Make the gem unstable until appropriately treated. It can still work as a capacitor, but without the infrastructure of the trap, which regulated and defused appropriately its power, the gem randomly discharges and/or interferes with nearby spells and magic items.

Fixing the gem in a suitable way could require a short side quest where the PCs find somebody that understand what that is (or are able to research it by themselves) and gather the required components to turn it into, say, an Eldritch Cannon that works as intended.

[DwarfFighter]

I figure it could serve as a power battery that can be installed into some other magical contraption. Perhaps the PCs can discover an inactive Golem and figure out that the gem can be installed into it to reactive it? Of course, they have no control of what the Golem will do when activated, but it does not necessarily have to be aggressive.

-DF

[Lupine]

What did the trap do

Basically, the original mechanism was one that stored the flow of magical energy, so that changes in ambient magic could be detected (there’s a strong theme in this setting between magic and portals. This machine was placed near a stable-ish shadowfell portal.)

The trap was when some sorcerer found the ruins this machine had been in, and modified it. The if triggered, the machine would now shoot int-save force damage magic bolts, doing 1d12 damage, that would drop dice types afterwards. (So, the next bolt would do a d10, and so on)

The players pulled the gem out of the machine, thereby stopping the partial circuit that caused the arcing.

[J-H]

So it's meant to work with another object, not on its own.

Crystal of Arcane Energy Storage
Uncommon
With 4 hours and the use of metalworking or jeweler's tools and 10gp worth of silver, this crystal can be attached to a melee weapon. An arcane spellcaster can expend a spell slot, charging it with magical energy that discharges on hit, similar to the effects of Magic Missile. The crystal can only be charged once fully discharged. When charged, it absorbs a number of charges equal to 5 + the level of the spell slot used. On its first hit against an enemy, the weapon deals extra force damage equal to the number of charges, consuming one charge.
Alternatively, it can be fastened to a Wand of Magic Missiles, doubling the effects of using additional wand charges to upcast.

So if you put a spell slot into it, it deals 6, then 5, then 4, then 3, then 2, then 1 force damage on hit, or a total of 21 points of force damage.

[Carlobrand]

Basically, the original mechanism was one that stored the flow of magical energy, so that changes in ambient magic could be detected (there’s a strong theme in this setting between magic and portals. This machine was placed near a stable-ish shadowfell portal.)

The trap was when some sorcerer found the ruins this machine had been in, and modified it. The if triggered, the machine would now shoot int-save force damage magic bolts, doing 1d12 damage, that would drop dice types afterwards. (So, the next bolt would do a d10, and so on)

The players pulled the gem out of the machine, thereby stopping the partial circuit that caused the arcing.

How specifically is it triggered? How does it target a victim once triggered? Presumably it still does the same thing, which means it could hypothetically still shoot at the person carrying it or go off while in the backpack, assuming the triggering condition was met.

[Lupine]

Well, y’all are welcome to keep thinking of ideas, if you want, but I ended up just saying it was a gem of brightness.

[Burley]

So, they broke the battery off of a trap? Neat. They have an arcane battery now. Maybe they can use it to activate arcane relics elsewhere (like a Zelda dungeon) or maybe it can be used to fuel certain spells to increase their duration (the wizard can attune and use it to make Mage Armor a 24hr spell).

Because they "broke" the trap, I wouldn't give them the damage part of the trap. Let them try things with it, but if they don't have a party member that'd be able to safely handle it (artificer, wizard, bard or cleric with high INT, etc), there'd certainly be danger involved if they tamper with it too much.

I sure do miss the Use Magic Device skill from 3.5.