D&D 5E mystic arcanum using lowlevel spell as arcanumspells?

[albatrossen]

Mystic Arcanum, I get it. BUT some other thing is not clear to me. PHB page 108 states :" choose one 6th level spell from the warlock spelllist as this arcanum." In the PHB page 201 it says "when a spellcastercasts a spell using a slot that is of a higher level than the spell, the spell assumes the higher level for that casting. For instance , if Umara casts magic missile using one of her 2nd level slots, that magic missile is 2nd level." Does this mean that I can choose to use a lower level spell n my mystic arcanum slots? Ex. I could put fireball in my 9th level arcanum slot and use it once every long rest to throw a fireball doing 14D6 damage but only once a day? or can I only choose the spells mentioned as level 9 spells on page 210 .

 

[The Crimson Binome]

I can definitely see where you're coming from on this. Consult your DM on this issue.

The most literal reading would say that the spell only assumes the higher spell level for the purpose of casting, and not for the purpose of something like Mystic Arcanum.

 

[Ashrym]

The answer is no. Warlocks don't have any spell slots higher than 5th level. Arcanum lets the warlock select a spell that can be cast once per long rest and does not give a higher level spell slot with which to cast any spells.

 

[Kobold Stew]

I can see a case whereby you could choose "Fireball" as your mystic arcanum and then ONLY be able to cast it at that particular level. Not RAW, of course, but as a DM I'd consider allowing it since by doing so you are foregoing access to any other spell at that level.

The mystic arcanum is such a delicate thing anyways: one choice, no take-backs: you are choosing the high-level power that your character is going to have, and it's irrevocable.

 

[Sword of Spirit]

There might be a bit of rules ambiguity, but I can't see any good reason (and I don't say that often) for a DM not to allow it, unless they are just trying to rule as conservatively strictly RAW as possible (ie, always going with the more restrictive reading when the rules are vague).

 

[Rocksome]

Personally, I think it's possible to choose Magic Missile as your 7th level spell. There are precedents where "spell level" refers to the slot used to cast the spell, so I see no reason to prevent a player making this choice.

 

[JackOfAllTirades]

This probably would not break the game. (And personally I like the idea.) But I think a wise DM would make this decision on a case by case basis.

 

[Sword of Spirit]

This probably would not break the game. (And personally I like the idea.) But I think a wise DM would make this decision on a case by case basis.

Out of curiosity, can you think of an example where it wouldn't be a good idea to allow it?

 

[Celtavian]

I'd be ok with it as a DM.

 

[JackOfAllTirades]

Out of curiosity, can you think of an example where it wouldn't be a good idea to allow it?

Not off the top of my head. However, it's been demonstrated that I'm not the most creative "game-breaker" in the 5E community, so I've learned to be cautious.

Edited to add:

I think the real worry here isn't anything on the Warlock spell list -- I don't see anything there I wouldn't approve of. I think the question is, would a spell acquired via multiclassing, or a feat such as Magic Initiate be eligible for Mystic Arcanum? That might get weird....