Divine Inspired Cantrip

[thedow]

Can someone tell me if this cantrip is too powerful or what else I could do to adjust it? Thanks!

Radiant Beam
Evocation Cantrip
- Casting Time: 1 action
- Range: 60 feet
- Components: V, S
- Duration: Instantaneous
You summon a beam of white holy energy from your god and fire it at a creature within range. Make a ranged spell attack against the target. On a hit, the target takes 1d8 radiant damage.
The more injured the target, the more susceptible they are to the effects of divine retribution. If the target is has taken damage, the beam deals 1d10 damage. If the target is below half hit points, the beam does 1d12 damage.
The spell’s damage increases by one die when you reach 5th level, 11th level, and 17th level.

[LibraryOgre]

I'd drop the damage to 1d6, 1d8 (damaged), 1d10 (bloodied). 1d10 damage cantrip is Eldritch Blast's bailiwick, and giving it every attack after the first pushes a bit close.

[Inevitability]

Compared to Toll the Dead, you're dealing slightly less damage (1d8 full/1d10 wounded/1d12 bloodied as opposed to 1d8 full/1d12 wounded) and delivering it through an attack roll rather than a wisdom save (Magic Resistance exists, but so do low-Wis enemies, so idk which is better). At the same time, you're delivering the damage with a much better damage type.

It's probably fine balance-wise, though you could nerf it if you wanted to. A bigger issue seems the conceptual overlap with an existent cantrip and the bookkeeping in keeping track of which enemies are below half health.

[Just to Browse]

Targeting low saves is usually better than targeting AC. In my experience, cantrips will more frequently be used to target enemies with low general defenses because the high-defense enemies are usually worth burning spell slots on instead. I evaluate Wis Save => Attack Roll as slightly worse.

Damage type is an interesting problem. Necrotic is on par with acid in terms of the raw number of creatures immune or resistant to it, while radiant damage is the 2nd best in these same terms (with the best type being force). Usually damage type doesn't matter that much for cantrips, because the expectation is that you will bring 2 complementary damaging cantrips on your adventures so you don't get locked out of a fight pokemon-style. But this is only true for the common damage types: acid, cold, fire, lightning, necrotic, poison. Any cantrip with a rare damage type gives you the opportunity to bypass this restriction. Force & Radiant practically guarantee you will only need 1 cantrip for the rest of your life, while Psychic & Thunder are slightly less of a guarantee (depending on how many animated objects vs magical floaty monsters you fight).

Side note: some folks consider necrotic an uncommonly-resisted damage type. That's not particularly true: necrotic is only slightly behind acid in terms of the number of creatures w/resistance and/or immunity to it. I think it's safer for designers to assume that necrotic is a common damage type when designing in a vacuum.

Cantrips with uncommon damage types usually hit 1 out of 3 of these properties:
They have notably worse damage than cantrips of a similar type (vicious mockery).
They require some unconventional tactic for the average mage (sword burst).
They are one of the best cantrips in the game (sacred flame).

Buuuut there's one more big caveat here, in line with the "you only need 1 cantrip" thing. Most cantrips with uncommon damage types also target saves! This is because, while targeting a save instead of AC is better on average, there will be times when you fight enemies who are all very dextrous / willful / sturdy, which will cut your base damage by 20%+ and make you wish you had a cantrip that targeted some complementary saving throw. Attack cantrips are more consistent. This is why eldritch blast is considered the best cantrip in the game: not only does it use the least-resisted damage type, it also targets the most generic defense, which means warlocks will only ever need 1 cantrip for the rest of their life.

So while the natural inclination is to compare this spell to toll the dead, I think the more natural comparison point is something like mind sliver, as it has comparable range and consistency. From the perspective of mind sliver, you are trading:
+1/tier damage at baseline
+2/tier damage to wounded enemies
+3/tier damage to bloodied enemies
Notably better damage type
(usual attack stuff) the rare chance to crit & the opportunity to gain advantage
in exchange for losing:
Targeting a notably weaker defense
-1d4 on the next saving throw within 1 round
(usual save stuff) no cover restrictions & the risk of getting disadvantage

I think this spell is comparable to mind sliver in terms of its consistency and power level. If you're looking to make a new default cantrip option for ranged clerics, I think you're in the right spot. But if you're looking or something competitive with toll the dead and sacred flame, I would tone the damage down a little.

If you do cut the damage down, I would argue for keeping the dice the same and just getting rid of the bloodied threshold. Tracking HP thresholds in real time is kind of annoying. I know 4e did it, but 4e was a tracking nightmare even with the assumption that mooks had (literally) 1 HP. With that shaved off, I think a player could reasonably choose between this and toll the dead depending on whether they want to trade consistency for less top-end damage.

One last note (sorry this post is so long). I think the rider effect here is a little incongruous with the flavor of the spell. Toll the dead is meant to be spooky death magic. Necromatic energies grasp at your enemy. If that enemy already has 1 foot in the grave, that grasp is tighter and colder. In contrast... why is a beam of holy light punishing the weak?