Warlock multiclassing into a spellcasting class - how to shift my level 1 spell over to my new class?

Question

As a high-level Warlock whose spell slots are 5th level I can have Warlock spells up to 5th level. But there are one or two 1st level spells that, while they don't scale with spell slot level, are so handy I haven't let them go.

But now I'm going to multiclass into a spellcasting class and get some 1st level spell slots along with the spellcasting feature. This new class has my favorite 1st level warlock spell on its spell list as well, so I'd obviously like to have my new class use that spell for one of my spells known and replace the Warlock spell known with a 5th level Warlock spell. I am struggling with how, especially by RAW, I can do this efficiently.

I can trade that spell away on my last Warlock level up, go a whole level without the spell, and then take it again when I multiclass. Or I could take it in my new class and have two versions of the same spell for a full level, and then trade out the Warlock version when I level up Warlock again. But ideally I'd make the swap right when I multiclass or the next time I level up as a Warlock without having either an overlap or a gap in spell coverage. And I'd like to do this in an ironclad, no trading "bending the rules for DM favors", way.

Is this possible and I'm missing it, or is there no way to do this?

Answer 1

You're out of luck

For Warlock the PHB states:

Additionally, when you gain a level in this class, you can choose one of the warlock spells you know and replace it with another spell from the warlock spell list, which also must be of a level for which you have spell slots.

So as you surmised in your question; you either drop the spell on the last level of being a Warlock and go without for one level, or you have it twice until you gain your next Warlock level.

I had the same issue with a Bard/Sorcerer. I wanted to drop a 1st level Sorcerer spell and gain it as a Bard. So for 3 levels, I had the same spell twice.

Answer 2

Scribe spell scrolls

When I multiclassed a sorcerer into cleric, I ran into a similar problem - I'd rather not have mage armor once I gain armor proficiency. I solved it by scribing a few scrolls of mage armor to tide me over.

XGE lists scribing spell scrolls as a downtime activity. The requirements for scribing a 1st level spell scroll are:

• The spell must be prepared or known.
• You must be proficient in Arcana.
• You must spend 1 day of work and 25 gp per scroll.

You'll want to make as many scrolls as you believe you'll require for one level. As with all downtime activities, it still requires DM permission. However, the activity requires no other special adjudication from your DM for small numbers of scrolls.¹ If you spend an entire workweek (5 days) scribing scrolls, there is a 10% chance of a complication.

Not all spells are good for scribing, however:

• Spells that don't scale with higher spell levels are perfect for scrolls.
• Spells that require a saving throw or attack roll make poor scrolls. A 1st-level spell scroll always uses a spell save DC of 13 and spell attack bonus of +5.
• Scrolls are more of a backup option. A scroll of comprehend languages or fog cloud is great to have for the rare cases you'll need it. Protection from evil and good that you cast four times per day in an undead campaign? Not so much.
• Reaction spells, like shield, may be tricky to work with.

Otherwise, you're out of luck. As others have pointed out, there isn't a way for you to do this that requires literally zero DM discretion.

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¹ If it helps your case, WotC's official organized play program, Adventurers League, allows players to use this activity without DM supervision.

Answer 3

You don't need to drop the Warlock spell at all.

RAW allows you to cast spells known from all classes using any spell slot you have. So, if you are a Warlock 9/Sorcerer 1 and you know the Sorcerer spell Burning hands, you could cast it at fifth level using a Warlock spell slot, and if you know the Warlock spell Comprehend Languages you could cast it using your first level spell slot.

So, just pick new spells from your new spellcasting class, and just keep the Warlock spell you like as a Warlock spell.

Relevant rules text from the Multiclass section:

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.