[RPG] Would it be game breaking to allow a Warlock to use his Mystic Arcanum to cast his spells at a higher level


I'm looking for ways to make the Warlock feel more flexible with his castings, and I like this solution, especially since it's limited by how few spellslots Warlocks have of higher level spells (essentially 1 for 6th level+).

Here's my proposed stipulations:

  • The Warlock can choose any spell he currently knows to cast at the level of Mystic Arcanum that he currently possesses (e.g. Cloud of Daggers, using his 6th level Mystic Arcanum.)
  • That Mystic Arcanum usage could only be regained upon long rests, a la RAW.
  • The Warlock would still only choose one spell per Mystic Arcanum that they learned.
  • The Warlock would also be able to 'upcast' his lower level Mystic Arcanums, should they allow it (e.g. Create Undead, at level 9).

Would this break the Warlock class in some way or have an overall negative impact if I allowed this?

For further clarity, the player has a Fiend Patron with a Pact of the Chain boon.

Best Answer

Would it "Break the Game"? Probably not

With only rare exceptions, lower-level spells that are upcast as higher level spells are weaker than spells native to the upcasted level. Giving a warlock the ability to upcast their regular spells (or other Mystic Arcanum spells) gives them some modestly improved flexibility, but it's pretty unlikely they'll be able to use it for some kind of absurd cheese, especially given that Warlocks already don't have a terribly robust list of spells. At the very least, it's unlikely a Warlock with this ability would be able to abuse a cheesy strategy worse than an equivalently leveled Sorcerer.

I am, however, of the opinion that it's probably not a good change. I don't know that balance considerations factor in so much as flavor considerations. Mystic Arcanum spells aren't just individual spells you have to cast like a 3.5ed!Wizard, but special spells granted to you by your patron. That is an important flavor difference between Warlocks and other casting classes, and I personally feel that it's important to preserve that flavor.

But like I said, mechanically, there's no real problem. This change makes Warlocks modestly more powerful, but they're not going to break the power level ceiling already established by 5e!Wizards from this change alone.