Does Confusion cast via the Dreadful Word invocation count as a warlock spell?

Question

From the answers over on the question of "What makes a spell being cast considered to be a {class} spell?", the implication is that something is a 'class spell' if it is on that class' spell list.

There is not, so far as I'm aware, any other general criteria for what makes something considered a warlock/wizard/etc. spell.

I am also under the impression that spending a warlock spell slot does not automatically make that spell a warlock spell, given the multiclassing rules allowing sorcerer/etc. spells to be cast via warlock spell slots.

While the rules state "To cast one of your warlock spells of 1st level or higher, you must expend a spell slot," and "The Warlock table shows how many spell slots you have to cast your warlock spells [...]", the phrasing of Dreadful Word could also be parsed as an instance of "specific beats general" enabling a non-warlock spell to be cast via warlock spell slots regardless of those rules (it is already enabling you to cast a spell you don't know, after all).

The multiclassing rules also give me the impression that spending a spell slot from a specific class- say, warlock- doesn't mean that the resulting spell is a warlock spell, anyways; you can cast sorcerer spells with pact magic slots, for example, and they still count as sorcerer spells.

So, the question: with a literal reading of the rules, since confusion is not on the warlock spell list, is confusion a warlock spell when cast via Dreadful Word for the purposes of Rod of the Pact Keeper?

I care about specifically a literal reading because it seems extremely clear that it should count as a warlock spell- there's no implication of what DC to use if you're not meant to use your warlock spell save DC ("Charisma is your spellcasting ability for your warlock spells"), for example. Crawford also confirms that to be the rules as intended- thanks, @Bloodcinder. I would never intend to argue otherwise in actual play. I'm just curious what the literal interpretation of the rules in this case results in, even if there truly is no rule indicating that it would be considered a warlock spell and it not being one seems nonsensical.

Answer 1

Invocation spells are Warlock spells for you and they benefit from Rod of the Pact Keeper.

By omission, the rules for invocation spells like confusion use your Warlock spell save DC. If that were not so, the class would mention what spell save DC to use instead. The rules as written define a spell save DC only once in the Warlock class: your Warlock spell save DC. So that's the one you use when you cast a spell through a Warlock feature requiring a saving throw. Nothing in the Warlock rules would suggest otherwise.

Regardless of what list a spell appears on, if a class feature tells you that you can cast a spell and the only way you can cast that spell is because you have that feature, then it's a class spell for you: literally, it is a spell based upon your class. By contrast, a spell you can only cast because you're a multiclass Sorcerer or because you're a Drow would not be a Warlock spell for you. So when you cast confusion using your invocation, you're casting one of your Warlock spells.

Therefore, yes, you benefit from Rod of the Pact Keeper's bonus to spell save DC when you cast confusion using an invocation. This reading is the simplest and most obvious.

Within the text of the Warlock class, the most straightforward and literal reading is that any spell it grants you is a Warlock spell for you, whether or not a particular shibboleth phrase declares that it is. Otherwise, if the term "class spell" were intended to be so rigorous and unintuitive as to exclude spells you can cast through your own class, we'd expect the term to be defined somewhere in the rules. It's not, so the rules as written default to the plain English meaning of the words. It's rules as written, not rules as legalistic.

Nevertheless, knowing the design intent doesn't hurt. The lead rules designer of 5e, Jeremy Crawford, confirmed this intention when I asked him about it on Twitter:

Me: If I am a Warlock and I use an invocation to cast a spell that's not on the Warlock list (such as Levitate, Confusion, or Slow) requiring a save, does it use my Warlock spell save DC? Also, can such a spell benefit from Rod of the Pact Keeper?

Crawford: The spells you cast through the Eldritch Invocations feature are meant to be warlock spells for you.

Crawford's tweets are not rules as written and are merely indicative of the design intent, but in this case it matches the simplest reading of the text.

Answer 2

It is not a Warlock spell and cannot benefit from Rod of the Pact Keeper.

Confusion is not on the Warlock spell list. It is also not 'made' a Warlock spell by the wording of Dreadful Word (c.f. Cleric Domain Spells). This has not been errata-ed. Therefore, RAW it isn't a Warlock spell.

The spell save DC is 8 + spellcasting modifier + proficiency bonus.

It is a Bard, Druid, Sorcerer, and Wizard spell so if you have levels in any of those classes you can use that class' spellcasting modifier (your choice if you have more than one). If you don't, your spellcasting modifier is 0.