Are there any serious balance issues with allowing all players to have access to elemental magic in my homebrew?

Question

The Background

I'm constructing a homebrew setting for a campaign in which elemental magic is much more common than in most D&D official settings.

There will be portals to the elemental planes and elemental creatures will be a common feature in the world.

To add flavour to the campaign, I want to provide adventurers (regardless of class) access to a few elemental features. I called it Elemental Affinity.

I intend to allow the players to choose one of the elements: air, earth, fire or water. Once chosen, they will not be able to change their chosen element – as, thematically, this will be something they would have grown up with as creatures born in this world.

I'm of two minds about providing this feature to NPCs from humanoid races and/or bosses but I think it would add flavour and a counter-balance perhaps, e.g. the leader and second-in-command of a large band of orcs may be Barbarians with an affinity to earth.

This is what I intend to provide my each of the players, for my homebrew:

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Elemental Affinity

Choose an element to which you have an affinity: air, earth, fire, or water. As you progress, your PC will acquire certain features depending on your overall character level.

Elemental Manipulation: At 1st Level you learn a Cantrip that does not deal damage and is associated with your elemental affinity:

• (air) Gust (XGE, p.157)
• (earth) Mold Earth (XGE, p.162)
• (fire) Control Flames (XGE, p.152)
• (water) Shape Water (XGE, p.164)

Elemental Bond: At 7th level, you can tap further into your elemental affinity. In combat, you can use your reaction to use this feature; this lasts until the end of your next turn. You can use this feature up to 3 times and you regain all your expended uses of Elemental Bond when you finish a long rest.

• (air) Resistance to lightning and thunder
• (earth) Resistance to poison; advantage on saving throws against petrification
• (fire) Resistance to fire
• (water) Resistance to cold and acid

Elemental Weaver: At 11th level, your connection to the elements becomes such that you begin to understand the very fabric of elemental magic. You learn a 6th-level spell associated with your elemental affinity. Once you have cast this spell, you regain the ability to do so when you finish a long rest. This feature does not use a spell-slot or count towards the total number of spells you know. (XGE, pp.159-160)

• (air) Investiture of Wind
• (earth) Investiture of Stone
• (fire) Investiture of Flame
• (water) Investiture of Ice

Note: Your spellcasting ability for the spell depends on your class: Charisma for bard, paladin, sorcerer, or warlock; Intelligence for artificer, wizard, fighter (eldritch knight, arcane archer, psi warrior), or rogue (arcane trickster); Wisdom for cleric, druid, monk or ranger. If you have more than one spellcasting ability, you choose which one to use for the purposes of this spell. If you are a melee class without a spellcasting ability, then use: Constitution for Barbarian or Fighter; Dexterity for Rogue.

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My question

Is allowing my players to have access the Elemental Affinity features (cantrips, resistance and investiture spell) likely to create any serious balance issues in the game - and potentially ruin the whole campaign?

What is a good answer?

For the purpose of an answer, it would be helpful if it followed the Good Subjective/Bad Subjective rule. I am looking for answers from DMs who have implemented a similar feature in their campaigns, or can see some obvious traps.

If you suggest an adjustment/substitute for one of the Elemental Affinity features for the purposes of rebalancing, please explain the reasoning behind it, too.

Answer 1

No

When people speak of balance in D&D 5e they usually have this in mind:

The actual balance in D&D 5e is more like this:

The players (almost) always win.

The game is biased so far in favour of the players that you have to try really, really hard to upset the balance. Adding things that make the players better isn't going to do that.

How this has worked for me

I haven't done what you are doing explicitly but, effectively, all you are doing is giving the players:

1. a free cantrip useful outside combat - so, less than a third as good as the Magic Initiate feat
2. something not quite as good as the Absorb Elements spell - which they could get with the Magic Initiate feat although they could only use that once.
3. A pretty cool but by no means an awesome 6th level spell they can use once a day.

So, all up, the equivalent of a medium-good magic item. Magic items don't unbalance the game. neither will this.

Based on my experience, most players will use 1. & 3. a few times and then forget they have them because giving up an action to use them is almost always worse than what they could do with whatever their primary class abilities give them.

No 2. is situational and won't make a great deal of difference - when they get hit with the right sort of element they'll use it, save a few hp of damage and feel cool.

Answer 2

No, because balance is always in your (the DM's) hands

I'm a new DM, but a long time player, and I've always been very particular about balance in D&D 5e, so take this answer with a grain of salt.

Something I realized while DMing is that the only balance that matters is balance between party members. Why? Because each player will want to feel like they contribute, either in combat or otherwise. Your player who is the face of the party, while also being both the skill monkey AND the tank and damage dealer, might have a great time, but I'm not sure your other players like getting overshadowed constantly. And our job as DMs is to make sure that everyone has a good time (don't forget about having fun yourself). Of course, there's a mandatory disclaimer that fun is subjective and players respond in different ways.

Since this is a party-wide buff, I don't believe it will present a problem for you. This is especially true in a homebrew campaign. Why? Because balance is always in your hands. If you feel like the party is too powerful for their level, you can try to have them face a more challenging encounter. There are some caveats to this, such as buffing damage output for both PCs and NPCs could make healing less effective in combat. So, let's take a look at your features.

Elemental Manipulation

This seems like it's purely for fun or flavor. No issue.

Elemental Bond

Resistance is nice, but situational. Getting them as a reaction for a turn, three times a day, is pretty okay... if it comes up. This is what I mean by balance is always in your hands. If you feel like it's difficult to challenge a 7th-level party using the elements, you can always challenge them in other ways. You can attack them with weapons, or even give your NPCs the Elemental Adept feat. Fair warning to not go too overboard with this as to make the feature obsolete. Throw them a few bone and let them use the feature from time to time, it's gonna feel good when it happens.

Elemental Weaver

This might be a different story, though. While I stand by my position in that balance is always in your hands, I will try to draw a picture on just how much this feature buffs a character. I will not cover how this will affect the classes that can get this spell anyway (Druids, Sorcerers, Warlocks, Wizards).

• The Barbarian is out of luck because he can't concentrate on anything while raging.
• Bards and Clerics typically have better spells to concentrate on. It can be situationally useful for half-casters (Artificers, Paladins, and Rangers), since they don't usually get access to Investiture spells, but many spells in their spell list are also fighting for concentration.
• Investiture of Fire and Investiture of Ice straight up gives you immunity to a damage type and resistance to another. While the option to use your action to attack using your elements won't be as attractive, this is a powerful defensive buff for classes that doesn't concentrate on anything (Fighters, Monks, Rogues). Investiture of Flame's additional benefit is particularly good for a frontliner, as creatures moving into melee will take damage. Make sure what your party's encountering can deal more than one damage type.
• Investiture of Stone's selling point is the resistance to physical nonmagical damage, everyone can benefit. Moving through walls is situationally useful too, Monks and Rogues could benefit more because of their ability to dash as a bonus action, useful to chase down elusive enemies, or even to run away. If you feel like the resistance is too powerful, you can give your NPCs magical weapons.
• For Investiture of Wind, 60ft. fly speed is amazing. Melee attacks can't reach, ranged attacks are at disadvantage, you'd be a kiting master. Archer builds like Fighters, and to a certain extent Rangers, wouldn't mind concentrating on this if it means that they can't be targeted by attacks. The only way to attack you is to target your saving throws. But be warned, Dex-main archer Paladins (which I have seen) can easily have high AC and saving throws through Aura of Protection.
• Lastly, it's still a spell, subject to Counterspell and Dispel Magic, and they only get it once a day. Which means you can totally shut it down using those methods too.

Now, if you feel like Elemental Affinity really adds to your game, and you're prepared to deal with these buffs, then I think there won't be any serious balance issues.