If you have the ability to cast a spell without a spell slot, can you cast that spell using a spell slot?

Question

A 10th level Drow warlock (for instance) has the following Drow Magic racial trait (PHB p. 24), in addition to its warlock spellcasting abilities:

You know the dancing lights cantrip. When you reach 3rd level, you can cast the faerie fire spell once per day. When you reach 5th level, you can also cast the darkness spell once per day. Charisma is your spellcasting ability for these spells.

Can the Drow warlock cast faerie fire (which is not on the warlock spell list) using a warlock spell slot?

Can it cast darkness (which is on the warlock spell list) using a warlock spell slot?

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The Sage Advice Compendium says this about the Magic Initiate feat:

If you’re a spellcaster, can you pick your own class when you gain the Magic Initiate feat? Yes, the feat doesn’t say you can’t. For example, if you’re a wizard and gain the Magic Initiate feat, you can choose wizard and thereby learn two more wizard cantrips and another 1st-level wizard spell.

If you have spell slots, can you use them to cast the 1st-level spell you learn with the Magic Initiate feat? Yes, but only if the class you pick for the feat is one of your classes. For example, if you pick sorcerer and you are a sorcerer, the Spellcasting feature for that class tells you that you can use your spell slots to cast the sorcerer spells you know, so you can use your spell slots to cast the 1st-level sorcerer spell you learn from Magic Initiate. Similarly, if you are a wizard and pick that class for the feat, you learn a 1st-level wizard spell, which you could add to your spellbook and subsequently prepare.

But this specifically requires you to pick the feat for one of your classes to be able to cast the spell learnt using your class spell slots, and does not seem directly applicable.

A Warlock can use warlock Pact Magic spell slots to cast spells learnt from levels of another spellcasting class, per the multiclass spellcasting rules (PHB p. 164):

If you have both the Spellcasting class feature and the Pact Magic class feature from the warlock class, you can use the spell slots you gain from the Pact Magic feature to cast spells you know or have prepared from classes with the Spellcasting class feature, and you can use the spell slots you gain from the Spellcasting class feature to cast warlock spells you know.

Similarly, if the warlock has learnt the invocation Mask of Many Faces (PHB p. 112)...

You can cast disguise self at will, without expending a spell slot.

...Can the warlock cast disguise self using a spell slot, e.g. to decrease the chance it can be dispelled?

Answer 1

No, you can't cast it using a spell slot.

Spells you can cast because of your race aren't spells you know, and thus can't be spells you prepare. Per the PHB (p. 201, "Known and Prepared Spells"):

Before a spellcaster can use a spell, he or she must have the spell firmly fixed in mind ...

... and it goes on to describe some of the class-specific variations of knowing and preparing spells. But in any case, having a feature from your race or class that allows you to cast a spell isn't the same as knowing the spell.

This is spelled out clearly in the multiclassing rules for Pact Magic quoted in the question (PHB p. 164; emphasis mine).

If you have both the Spellcasting class feature and the Pact Magic class feature from the warlock class, you can use the spell slots you gain from the Pact Magic feature to cast spells you know or have prepared from classes with the Spellcasting class feature, and you can use the spell slots you gain from the Spellcasting class feature to cast warlock spells you know.

Likewise, the Drow Magic trait clearly distinguishes the known cantrip from the merely castable other spells (PHB, p. 24; bold for emphasis mine):

You know the dancing lights cantrip. When you reach 3rd level, you can cast the faerie fire spell once per day. When you reach 5th level, you can also cast the darkness spell once per day. Charisma is your spellcasting ability for these spells.

If the intent of the rules was that Drow also knew the non-cantrip spells, it would say so.

Answer 2

You can only use spell slots on a spell gained from a feature if it is a class spell for you and the spell is either known/learned or prepared

(Besides magic items) A spell must be known/learned or prepared in order to use spell slots to cast it

The "Known and Prepared Spells" section states:

Before a spellcaster can use a spell, he or she must have the spell firmly fixed in mind, or must have access to the spell in a magic item. [...]

[...] In every case, the number of spells a caster can have fixed in mind at any given time depends on the character's level.

These quotes establish that casting a spell requires it to be known/learned or prepared and not merely be cast-able without the use of spell slots.

For this reason, features such as Drow Magic's darkness or faerie fire cannot be cast using spell slots; these spells are not known/learned or prepared despite being cast-able:

You know the dancing lights cantrip. When you reach 3rd level, you can cast the faerie fire spell once per day. When you reach 5th level, you can also cast the darkness spell once per day. Charisma is your spellcasting ability for these spells.

Note that this also means that if a feature makes a spell learned/known but you class prepares spells then you still cannot cast it because a class which prepares spells can only cast spells that they have prepared, not merely known/learned.

Even if a spell from a feature is known/learned or prepared, spell slots can only be used to cast spells that are associated with (one of) your class(es)

The Players Handbook has received errata changing the wordings of every Spellcasting and Pact Magic feature (the example below is for Sorcerers with the pre-errata quote followed by the post-errata one):

The sorcerer table shows how many spell slots you have to cast your spells of 1st level and higher.

The sorcerer table shows how many spell slots you have to cast your sorcerer spells of 1st level and higher.

Thus, the spell slots provided by a class can only be used to cast spells from/of that class. They cannot be used to cast spells that are not considered their own class spells.

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How do you know if a spell is associated with (one of) you class(es)?

The following three Q/A's (one is closed as a duplicate) have differing answers:

• What makes a spell being cast considered to be a {class} spell?
• Are spells learned from feats considered to be associated with your class?
• If I am a Celestial Warlock and I take the Magic Initiate - Cleric (Cure Wounds), does that now count as a Warlock spell for me?

It seems inconclusive then, and that a GM could have to rule whether or not misty step (which appears on the sorcerer spell list) counts as a sorcerer spell when it is obtained through something like the the Fey Teleportation feat discussed elsewhere:

You learn the misty step spell and can cast it once without expending a spell slot. You regain the ability to cast it in this way when you finish a short or long rest.

Thus misty step is considered a learned/known spell but whether or not it is also considered a sorcerer spell will come down to a GM decision.

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Wizard might be an exception to all this

The Sage Advice Compendium states:

Q. If you have spell slots, can you use them to cast the 1st level spell you learn with the Magic Initiate feat?

A. Yes, but only if the class you pick for the feat is one of your classes. For example, if you pick sorcerer and you are a sorcerer, the Spellcasting feature for that class tells you that you can use your spell slots to cast the sorcerer spells you know, so you can use your spell slots to cast the 1st-level sorcerer spell you learn from Magic Initiate. Similarly, if you are a wizard and pick that class for the feat, you learn a 1st-level wizard spell, which you could add to your spellbook and subsequently prepare.

In short, you must follow your character’s normal spellcasting rules, which determine whether you can expend spell slots on the 1st-level spell you learn from Magic Initiate.

There's a lot in there, but the bolded section is what I'd like to point out. Somehow if a Wizard knows a spell they might be able to add it into their spellbook and thus prepare that spell. The SAC doesn't exactly explain why a Wizard can do this, but it seems that they could. Perhaps they turn it into a spell scroll first or something similar.

Answer 3

Not if you stick to RAW, but the clear trend is against current RAW.

The other answers have done an amazing job of explaining RAW, so I won't rehash that, but it is telling that ALL of the new "you can cast x spell" feats and abilities have been tagged "you can also cast with any spell slots you have". The newer abilities are almost all stronger than the old ones too!

Yes they could have been clearer and released an errata, but there are so many dodgy rules they haven't clarified yet that if we assume no errata = intended then we will be playing some very odd games. Plus they have a job to do, which is to make money, and faffing on with errata like this probably would never get high up the priority list.

The new addendum to the similar abilities is 100% in my view and admission that there is not only nothing wrong with allowing them to be cast with slots, but that it was intended all along and they are just finally correcting it.

Also I am not a fan of sticking to RAW just because, and where is the logic in being able to cast a spell and not being able to cast the spell at the same time? Just let it happen.

Answer 4

Only if the feature explicitly says so

As explained in other answers, the case for the original Drow Magic trait is that no, you cannot cast those spells using spell slots, because you don’t “know” them in the context of your class. It’s not a wizard/sorcerer/cleric etc spell, so you can’t cast it with the Spellcasting (or Pact Magic) feature you get from your class.

A helpful way to think about this is that mechanically you are casting a spell, but narratively you are using an innate magical ability common to your species. This is often called out by making exceptions to the normal rules, for example Githzerai use of mage hand. From the updated version of the race in Mordenkainen Presents: Monsters of the Multiverse:

Githzerai Psionics

You know the mage hand cantrip, and the hand is invisible when you cast the cantrip with this trait.

Making it invisible allows existing mechanics to model minor telekinesis.

Since the question was asked, however, other races, updates to existing ones and even feats have granted the ability to cast a spell without a slot once per day, and explicitly allowed the spell to be used with spell slots as well. To use the updated Githzerai as an example again, the Githzerai Psionics trait continues (emphasis mine):

Starting at 3rd level, you can cast the shield spell with this trait. Starting at 5th level, you can also cast the detect thoughts spell with it. Once you cast shield or detect thoughts with this trait, you can’t cast that spell with it again until you finish a long rest. You can also cast either of those spells using any spell slots you have of the appropriate level.

Note that the extra utility of using the spells with spell slots is balanced by the fact that you only get one free cast of either spell per day, not one free casting of each one.

Most of the races with innate spells from sources published after the Players Handbook have had their traits similarly updated to allow them to use them with spell slots, with the same limitation. The ”Character Origins” playtest document for One D&D indicates it’s likely that will also be the case for races from the Players Handbook in the 2024 version as well.

But if you’re playing with the original PHB version of the Drow (or Tiefling), you are out of luck - though you have a model and a good case for asking your DM to make a ruling allowing use of your Drow Magic spells with your spell slots.

Answer 5

Yes, you can cast it using a spell slot.

Spells you can cast because of your race are spells you know, and thus can be spells you prepare.

This works essentially the same way as if you had gained access to this spell through multi-classing.