What level should Elemental Bane be to be balanced?

Question

Elemental Bane from Xanathar's Guide to Everything seems high to me at fourth level.

For a spell pick, a preparation slot, a fourth level spell slot, a full action and concentration, you get a spell that has the easiest save in Constitution, and if the target fails, it does nothing by itself. You must also manage to hit the target with some elemental damage for it to do something. If you do, you get an expected grand total of 7 extra damage for all your efforts. Against a single target, unless you prefer to upcast it to an even higher level.

You can get these 7 extra every round for the rest of the fight, and you also can strip the target of a damage resistance, so maybe if you have a campaign with lots of resistant enemies and no good choices for your elemental damage spells it might be worth it? Assuming this were a homebrew spell, what level should this be to be in line with the other spells in the game?

For answers that highlight cumulating effects of the resulting damage from advantageous situational settings, it would be useful to consider the opportunity cost of the damage caused by casting a fourth level damaging spell such as blight instead, which deals 8d8 necrotic damage directly on a failed Constitution save.

Answer 1

That's not how Elemental Bane works

Choose one creature you can see within range, and choose one of the following damage types: acid, cold, fire, lightning, or thunder. The target must succeed on a Constitution saving throw or be affected by the spell for its duration. The first time each turn the affected target takes damage of the chosen type, the target takes an extra 2d6 damage of that type. Moreover, the target loses any resistance to that damage type until the spell ends.

We have our adventuring band of Sid, Marty, and Croft. Our band encounters a Glabrezu which has resistance to fire damage. That means Sid's scorching ray spell, Marty's Flame Tongue, and Croft's flame blade spell are all going to do only half damage, making this a tough fight. But Sid has an idea...Elemental Bane

The important bits are:

1. It removes a creature's resistance to an elemental damage type
2. It adds extra damage, per turn, not per round
3. It doesn't have to be the caster's damage

So if target fails that one saving throw (I know, Constitution saves are tough), all attacks that do {named damage type} damage hit extra hard.

That means, if the Glabrezu fails, the first ray of scorching ray will do an extra 2d6. Marty's Flame Tongue sword, if it does fire damage, will do an extra 2d6, and Croft's flame blade, if it hits, will do an extra 2d6 damage. And, because the spell removed the resistance factor, ALL of that extra damage, plus the instigating damage, are at full strength, not reduced by half.

This means 8d6 (scorching ray) + 4d6 (flame tongue) + 5d6 (flame blade) of fire damage, instead of the resisted 3d6 (scorching ray) + 1d6 (flame tongue) + 1.5d6 (flame blade). 17d6 vs 5.5d6 means you have single-handedly tripled your party's damage output.

There is also no further saving throw, so until Sid loses concentration, that's going to work for the whole battle.

So, given all it can do, although situational¹, it's fine as a 4th level spell

Elemental Bane is unique in its features so there is no way to do a direct comparison. But there are spells that do "similar" things. Consider this list of other 4th level spells:

• Banishment
• Confusion
• Phantasmal Killer

These are all 4th-level, concentration spells with a single target. They all are debilitating to the target in some fashion or another. Banishment takes out a target entirely, but for only a minute if they are native to the current plane. Confusion can make a target do nothing for its turn. And Phantasmal Killer gives the frightened condition along with a bunch of damage per round.

Since you added a bit about "cumulating effects of the resulting damage from advantageous situational settings"

In my above example, yes, the first round Sid would not cause any damage, so the numbers given would only be in full effect when Sid got their next turn. So, based on the theory that fights last three rounds, the damage would look like:

• Round 1: 0 (Sid; 4th level elemental bane) + 4d6 (Marty; plus whatever sword damage) + 5d6 (Croft) = 9d6
• Round 2: 8d6 (Sid; 4th level scorching ray) + 4d6 (Marty; plus whatever sword damage) + 5d6 (Croft) = 17d6
• Round 3: 8d6 (Sid; 4th level scorching ray) + 4d6 (Marty; plus whatever sword damage) + 5d6 (Croft) = 17d6

For a total of 43d6 damage, or about 150ish.

Whereas if Sid kept casting blight:

• Round 1: 8d8 (Sid; 4th level blight) + 1d6 (Marty; plus whatever sword damage) + 1.5d6 (Croft) = 8d8 + 2.5d6
• Round 2: 8d8 (Sid; 4th level blight) + 1d6 (Marty; plus whatever sword damage) + 1.5d6 (Croft) = 8d8 + 2.5d6
• Round 3: 8d8 (Sid; 4th level blight) + 1d6 (Marty; plus whatever sword damage) + 1.5d6 (Croft) = 8d8 + 2.5d6

For a total of 24d8 + 7.5d6 damage, or about 134ish.

For a grand different of 16ish points of damage difference in favor of elemental bane!

Now, this is all based on the premise that all attacks hit, the Glabrezu failed their saving throw against elemental bane, no one goes unconscious during the battle, and other factors. But if the party has a lot of fire based damage, and the situation is right, elemental bane can bring a lot of extra fire power (intentional) to a party.

And here are some other factors:

• blight is a saving throw spell; not an attack. Meaning instead of one saving throw against Constitution, it will be three. Against the Constitution ability you didn't like in the first place. So there is potential that at least one of the blight spells is going to only be half damage.
• scorching ray, along with Flame Tongue and flame blade are attack rolls, meaning there is potential for one or more critical hits doubling the extra damage that is no longer resisted.
• Marty is most likely a Fighter-type class, and by the time Sid can cast multiple 4th-level spells, would most likely have at least one extra attack if not two extra attacks. This pumps up the damage potential/difference even greater.

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¹ Every spell is situational, just some apply to fewer situations than others. Revivify only works on people that have been dead for less than a minute, but it's still a really good spell to have when the situation occurs.

Answer 2

Its application is niche, but it is uniquely good at what it does.

I'm going to tell you that 4th level is just fine for this spell. Your understanding of this spell's power seems a bit skewed by how bad it is when you use it wrong. But we shouldn't judge a spell's power based on using it wrong. We should judge a spell's power based on how good it is when it is used right.

Specifically, elemental bane neutralizes a target's resistance to the chosen damage type, and amplifies damage dealt of that type. If the target does not have resistance to the chosen type, of course the spell doesn't do anything for you beyond the meager 2d6 damage it offers if you happen to hit the target with that damage type. But what if you know you are going to face a foe with resistance to fire damage and you are a wizard specializing in fire evocations? You've just more than doubled your damage output. Your fireball just went from 4d6 to 10d6. Your scorching ray just went from 3d6 to 8d6. It works even better when the target has a whole host of resistances, and you can plan around only needing to neutralize one of them.

When it works, it works really well, and it is the only spell that does what it does. It's fine at 4th level. You're just considering its power in the wrong context.

Answer 3

For a relatively optimized party, there isn't a level where it is balanced (or even worth using).

The optimal situation to use Elemental Bane is when you have a group of people using elemental attacks against a single target, the attacks will continue for some time (aka the target has a lot of hp, or the attacks do very little damage on their own), the target has Resistance to that elemental type, and that target fails the Constitution saving throw.

If a target has a low constitution saving throw, it typically will not have a huge amount of hp. Enough hp to last dozens of attacks and a good con save are often correlated.

D&D parties typically don't do 'very little' damage with their attacks (when they can help it), and often don't do the same damage type - the barbarian does Slashing, not Fire, again, usually.

Single enemies fighting against a 7th level D&D party often have very good saves, legendary resistances, or if they lack these traits are not tough encounters that a 7th level spellcaster should use a 4th level spell slot to defeat.

An optimized party will generally try to have access to multiple damage types, and when facing against an opponent roll Arcana, Nature, or Religion to try to recall if it resists fire or is weak to sunlight or what have you. Likewise many DMs allow players to work out if a target is resistant or immune to a type of damage by that foe's reaction to eg. being shot with flames (if they don't get burned that's a good clue).

Ergo outside people blithely applying it to things like 'maximum damage challenges', Elemental Bane is not going to be optimal for the majority of situations that a D&D party finds themselves in. A situation where a 7th level spellcaster and a gaggle of firebolt using apprentices face off against a fire-resistant demon would be a great situation for Elemental Bane, but that is not the typical D&D party composition.

A less optimized (Bob the Sorcerer only ever chooses Fire spells) and caster-heavy dnd party, especially a larger one (6+ players) where the DM has artificially inflated monster HP without changing other stats, and treats fights as slugfests (intelligent enemies do not use traps, tactics, magic items or spells but instead wade into melee and attack at random or only hit the full plate + shield tank over and over again etc), with a party that either is outright told that the creature is resistant as opposed to immune or metagames, will potentially see Elemental Bane outperform other spells - likewise in a situation where the party has multiple elemental-damage using allies (summoned via Planar Binding or other methods) it will do a lot better.

(Situations with high-hp but otherwise unimpressive stats enemies and unoptimized parties are more common than you'd think in 5e - often hp was inflated as a method to make fights 'last longer', or at least that's what I assume based on complaints about fight length on various forums and the suggested solutions to make them last longer. That advice and complaint has been tapering off considerably, and now the opinion on various forums seems to weigh heavily against this form of length-padding meaning that it is likely less common than in the early years of 5e's existence (again, judging by forum posts on the topic). But it probably still exists especially in DMs who started DMing in early 5e era with their style informed by the mode of that time period.)

However even in this ideal environment, elemental bane is not necessarily better than a summon spell upcast to 4th level, or a spell like Hold Person or Fear which has a very meaningful effect on a failed save, in some cases effectively defeating the enemy. Even with a situation of high hp low stats enemy, unoptimized party who all use the same elemental damage type etc, it could still be worse than another spell cast out of a 4th level slot.

Thus, overall Elemental Bane is a very weak spell. In its ideal environment, it's still a maybe. In a typical environment, it's very rarely going to be a good idea. In an optimized party that uses common tactics like 'not casting fire spells against the fire resistant enemy', it is unlikely to be a good idea to use.

Even if it was a 1st level spell, the Action cost is likely better spent elsewhere. Having a chance to add a bit of extra damage and ignore a resistance is just too situational, it relies on a party with the right elemental damage type, and it relies on knowing the creature is resistant (and not say, Immune).

The level at which it is best balanced is fairly unknowable. The party of 8 characters fighting a 167hp guy who resists everything and does 1d8+4 damage is probably a thing and in that milieu a 2nd level spell that gets rid of a resist and adds 2d6 damage to their 1d8 cantrips is probably pretty great. In a more optimized group fighting lower-hp, higher-saved, and much higher damage foes, a 2nd level spell that does that is mostly going to be a waste of a turn.

It unfortunately interacts with 'how optimized is the party' and 'how fight-padding is your DM' and those are big deals for 5e and very variable matters of tone and table style which will hugely inform the balance point of the spell.