How powerful is a "Breathe Air" spell?

Question

Land-dwelling druids can figure out a way to use magic in order to breathe underwater (, provided that they are able to cast 3rd-level spells). But what about druids that are already able to breathe underwater, but not on land? Of course, they would have no need for the water breathing spell. (Unless they have some friends who rely on air). Instead, they would probably be more interested in a spell, which allows oneself to breathe air.

I am considering homebrewing a spell that would be 100% identical to water breathing, except instead of saying 'the ability to breathe underwater' it would say 'the ability to breathe air'.

Would a spell like that be more, less or equally powerful as water breathing. Consequentially, would such a spell be 3rd-level as well, or should it require a lower/higher level spell slot.

My players will encounter such a druid and I have to estimate how mighty this NPC has to be, in order to cast such a spell.

Answer 1

It should probably be a 3rd level spell

There aren't really any good guidelines for this. Spell effects are normally the reference frame for other effects and custom spells and it is not very clear what kind of "empowerment" this is.

The best analysis we can do is for what the spell effectively does, which is allowing access to a area across the water-air barrier (without the risk of suffocation). Thus the "breathe air" spell would have exactly the same strength as the water breathing spell and should be of the same level.

From this point of view, a higher level spell with a comparable effect would be plane shift (7th level) which allows access to other planes which is quite clearly a more powerful effect.

A piece of advice from the DMG you proposed spell arguably runs afoul of is:

Avoid spells that have very limited use, such as one that works only against good dragons. Though such a spell could exist in the world, few characters will bother to learn or prepare it unless they know in advance that doing so will be worthwhile.

--- Dungeon Master's Guide p. 283

However as this spell is intended for an NPC specifically it should not be much concern.

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As a side note a spell which only allows the caster to breathe air should - for the reasons given above - be a 2nd level as it is then more comparable to alter self (which as one of its modes can give the caster water breathing and a swimming speed).

Answer 2

It should be a lower level spell

Spells should take into account how strong/useful they are to the players when calculating their level. Unfortunately, I was also not able to find any concrete guidance for this in the rules, so I resorted to existing spells and their levels to determine my answer.

Consider the Light cantrip as a basic example. It is a level 0 spell that provides a magical source of light similar in intensity to that of a torch. Since a light source is primarily beneficial for PC and monster alike, and the effect can be duplicated with a mundane item, it is placed pretty low on the power scale. But if we were to invert the effect, light to darkness, suddenly it becomes a level 2 spell. Why? Because blindness is pretty effective as a control tool at lower levels, as many players and monsters lack tools to deal with it.

So to circle back to the Breathe Air spell, it's power ranking should be determined by how useful it will be to the players in your campaign. Assuming your party is composed of people who usually breathe air, this spell does very little for them, and will likely rarely come up outside of the NPC you created. If, however, you plan on introducing a whole society of water breathing casters, then an argument could be made for keeping the spell at its counterpart's level.

Answer 3

If it acts like water breathing I would keep the same level as water breathing.

If it is more restrictive (self-only, no ritual casting, more expensive to use, etc.), then I would lower the level based on the change.

If it were less restrictive (effects more targets, easier to cast, adds extra effects other then breathing, etc) than I would raise the level based on the additional benefit the spell offers.

As described above I would leave it the same level as water breathing.

I personally wouldn't even make a new spell, but rule that the current one could be used in such situations for the same effect.

I also wanted to point to DMG page 283, which has this to say about creating spells:

When creating a new spell, use existing spells as guidelines.

Here are some things to consider:

• If a spell is so good that a caster would want to use it all the time, it might be too powerful for its level.
• A long duration or large area can make up for a lesser effect, depending on the spell.
• Avoid spells that have very limited use, such as one that works only against good dragons. Though such a spell could exist in the world, few characters will bother to learn or prepare it unless they know in advance that doing so will be worthwhile.
• Make sure the spell fits with the identity of the class. Wizards and sorcerers don"t typically have access to healing spells, for example, and adding a healing spell to the wizard class list would step on the cleric's turf.

Following this I would specifically emphasize the following:

When creating a new spell, use existing spells as guidelines.

In this case, water breathing - and:

Avoid spells that have very limited use

Unless the spell will have a larger presence, such as a game where water creatures are commonly needing it, then it would be better covered by allowing the water breathing spell to work for this purpose instead of making a new spell for the effect.