Is this cantrip "shoot confetti" balanced with the PHB cantrips?

Question

In the process of promoting silly party feats and a cantrip to support one of those feats, I designed:

Shoot Confetti
cantrip, conjuration
Range: 30 ft
Casting time: 1 action
Duration: Instantaneous
Components: S, V
Class: Bard, Warlock, Wizard

You point one of your fingers in a direction away from you. A stream of confetti bursts forth to a point within 30' of you, lightly obscuring a volume no larger than a 5' cube for 1d4 rounds. You can have two of these effects present at any one time.

The confetti is flammable: mundane fire (torches, matches, burning tapers, candles, etc) and spells such as fire bolt that set fire to flammable materials burn the confetti away and in so doing cause 1d4 fire damage. This fire damage is increased to 2d4 at 5th level, 3d4 at 11th level, and 4d4 at 17th level.

Like vicious mockery, it has two different effects, but it isn't a powerful damage dealer. In order to do damage, either the bard or the ally must take a subsequent action. The opportunity for accidental damage is certainly present.

Is this cantrip within the bound/constraints of cantrips in the PHB?
If not, what adjustment needs to be made to bring it into balance?

Notes:

1. The chosen volume is similar in size to minor illusion and shape water cantrips.
2. The "something else catches it on fire" is similar to what happens to a web when a fire bolt, flaming sphere, or a fireball hits the webbed area.
3. I was considering making this a bonus action cantrip, but I got the idea that an exploit like shoot confetti/firebolt as bonus action/action would be a 'too powerful' exploit and chose '1 action' instead.
4. If I can get this cantrip right, I'll be adding it to the Wild Beyond the Witchlight adventure.
5. I am not sure if the name wholly captures the cantrip; if a recommendation for a new name like "confetti cloud" or something else comes to mind when offering an answer, a better name would be appreciated but is not necessary to answering the balance question.

Answer 1

Clearly overpowered

Character can cast it with one hand while keeping a torch in front of him with the other. Guaranteed damage without attack roll and save is too much.

either the bard or the ally must take a subsequent action

That is not consistent with how the cantrip is written now. Fire just lights it up so there is no need to take an action. If not played on the grid, all is needed is a bit of movement that will take the flame of a torch in contact with the confetti.

In a way, it is even more powerful than the Web spell. Burning Web only damages creatures that starts their turn in it. Allies can still pull the creature out before it gets hurt. There is no defense against burning confetti at all.

If you want to model it after Web, make it burn away in one round and only damage creatures that starts their turn in the fire. Still, this is mechanics designed for 2nd level spell. I believe that a more mundane Dexterity saving throw would be more appropriate for a cantrip.

The fact that is only a 1d4 does not compensate well. If chance to save is about half, then Thunderclap's 1d6 damage is worth on average 1.75, and confetti's 1d4 is worth on average 2.5 damage. Clear win for Confetti - and Confetti, in addition to being superior damage dealer, has added flexibility.

Answer 2

This is likely very weak and has some unusual decisions

Light Obscurement is rarely useful

The shoot confetti spell causes a single 5x5 cube to become lightly obscured and we know the following from the rules on Vision and Light:

[...] In a lightly obscured area [...] creatures have disadvantage on Wisdom (Perception) checks that rely on sight. [...]

For an extreme majority of cases, this simply won't be a factor; creatures can leave the space easily given its size and creatures rarely make Perception checks which would have to happen at exactly that moment while in that space.

The duration (1d4 rounds) is unusual

Additionally, the area lasts for 1d4 rounds; this is, as far as I know, unheard of in a cantrip or other spells. I can't imagine increasing the duration to 1 minute, or even 1 hour, would have any negative effects and it would, if anything, make the weak cantrip stronger.

The damage is unreliable, automatic, and despite that, is outpaced by other cantrips

Damaging with this cantrip requires the creature not to leave the area before you are able to use fire to cause the automatic 1d4 damage. We can actually directly compare the damage output to fire-bolt (H is hit chance, C is crit chance):

1d4 vs 1d10 (H) + 2d10 (C)
2.5 vs 5.5H + 11(0.05)
2.5 vs 5.5H + .55
1.95 vs 5.5H
0.35 vs H

So if you can hit on a die roll of 13, fire-bolt is the better choice. If we do out the math for other levels, this die roll requirement stays the same. So shoot confetti is almost always worse than fire-bolt (which also has quadruple the range). And this doesn't even account for the fact that the expected damage of shoot confetti actually is not 1d4; it's 1d4 times the chance you actually damage somebody, which is certainly less than 100%.

The torch/fire interaction/requirement is unclear

It's unclear to me how this works: Can a creature just walk up to the confetti while holding a torch and it combusts? Does the torch need to be thrown? Does igniting it with a hand-held torch cause the torch bearer to take the damage as well? Can a fire-bolt merely travel through the confetti or must it hit something in it?

Putting it all together

The light obscurement is rarely useful, the damage is almost always worse than just using fire-bolt, it has a few oddities (1d4 round duration and automatic, save-free damage), and how exactly the confetti combustion works is under-defined/unclear. Overall I would call this cantrip very weak.

Answer 3

Much depends on the application of "burns the confetti away".

It would be overpowered to have a torch in one hand, cast the cantrip with the other, and have a 30' long, 5' wide ray of fire damage with no save and no hit roll. However, my reading of the spell would indicate that in this situation, the stream of confetti would ignite in the square of the torch holder (caster), damage them, and then be burned away by the time it hit the target square, for no damage to the target but perhaps a gust of hot wind. This reading would not be overpowered. It does mean that casting the spell could take advantage of someone else holding or standing next to a flame source, but since such targets of opportunity are situational, I do not consider that overpowered.

Similarly, you could target a square within 30 feet, start the confetti cloud, and then 'walk over and ignite it' with no save and no hit roll. But this is analogous to walking over, pouring out (not throwing) an oil flask, and then igniting it for automatic damage without a hit roll or save. You can do that, but the risk to a caster of voluntarily putting themselves within an opponent's reach balances out the 'automatic' damage, which is low. This is also not overpowered. And since this burns away the confetti, my reading is that it would end the duration of the spell if it had turns remaining.

Lightly obscured can have interesting interactions

Such a small area of effect means that it will be little use in partially blinding an opponent; they can just leave the area. But it could see use in obscuring an object, oneself, or an ally. Suppose you, a clown-fairy, have the party trapped inside your circus wagon with the only way out a secret door. Your ally, a rat-fairy, is currently Hidden and moving in to Sneak Attack one of them. On your turn you ready an action to cast your cantrip.

Your ally steps on a squeaky floorboard, threatening to give himself away (low Stealth roll)? Shoot the confetti at his target, dropping their Passive Perception by 5 from disadvantage and maybe preserving your ally's Hide.

The party starts to Investigate the wall of the wagon, looking for the secret door before you are done monologuing? Shoot the confetti at the wall to disadvantage their Investigation roll while you say, "It's not over there!"

The party tries to make an Insight on you to see how seriously to take your monologue? Confetti yourself to disadvantage their Insight.

Also, wild elves get 'mask of the wild' that allows them to hide when lightly obscured by natural conditions. As a DM, give 'mask of the wild beyond the witchlight' to all your clown-fairies, so they can confetti themselves before Hiding, as the equivalent of a ninja smoke-bomb. Poof! you're gone!